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• SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28

  - by pinaldave

  The key Dynamic Management View (DMV) that helps us to understand wait stats is sys.dm_os_wait_stats; this DMV gives us all the information that we need to know regarding wait stats. However, the interpretation is left to us. This is a challenge as understanding wait stats can often be quite tricky. Anyway, we will cover few wait stats in one of the future articles. Today we will go over the basic understanding of the DMV. The Official Book OnLine Reference for DMV is over here: sys.dm_os_wait_stats. I suggest you all to refer this for all the accuracy. Following is a statement from the online book: “Specific types of wait times during query execution can indicate bottlenecks or stall points within the query. Similarly, high wait times, or wait counts server wide can indicate bottlenecks or hot spots in interaction query interactions within the server instance.” This is the statement which has inspired me to write this series. Let us first run the following statement from DMV. SELECT * FROM sys.dm_os_wait_stats ORDER BY wait_time_ms DESC GO Above statement will show us few of the columns. Here it is quick explanation of each of the column. wait_type – this is the name of the wait type. There can be three different kinds of wait types – resource, queue and external. waiting_tasks_count – this incremental counter is a good indication of frequent the wait is happening. If this number is very high, it is good indication for us to investigate that particular wait type. It is quite possible that the wait time is considerably low, but the frequency of the wait is much high. wait_time_ms – this is total wait accumulated for any type of wait. This is the total wait time and includes singal_wait_time_ms. max_wait_time_ms – this indicates the maximum wait type ever occurred for that particular wait type. Using this, one can estimate the intensity of the wait type in past. Again, it is not necessary that this max wait time will occur every time; so do not over invest yourself here. signal_wait_time_ms – this is the wait time when thread is marked as runnable and it gets to the running state. If the runnable queue is very long, you will find that this wait time becomes high. Additionally, please note that this DMV does not show current wait type or wait stats. This is cumulative view of the all the wait stats since server (instance) restarted or wait stats have been cleared. In future blog post, we will also cover two more DMVs which can be helpful to identify wait-related issues. ?sys.dm_os_waiting_tasks sys.dm_exec_requests Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Top 10 “Ease of Use” Features of expressor Studio

  - by pinaldave

  expressor Studio is new data integration platform that is being marketed as the most easy to use tool of its kind.  But “easy to use” can be a relative term – an expert can find a very complex system easy, but a beginner might be stumped.  A recent article online discussed exactly what makes expressor Studio so easy use, and here is my view on this subject. Simple Installation There is one pop-up for one .exe file, and nothing more.  You can’t get much simpler than this.  It is also in the familiar Windows design, so there should be no surprises. No 3rd party software dependency Have you ever tried to download software, only to be slowed down by the need to download a compatible system to run the program, and another to read the user manual, and so on?  expressor Studio was designed specifically to avoid this problem. Microsoft Office Like Ribbon Bar and Menus As mentioned before, everything is in the familiar Windows design, from the pop up windows to the tool bars and menus.  There should be no learning curve for using this program, or even simply trying to navigate around a new system. General Development Design Interface This software has been designed to be simple and straightforward.  Projects can be arranged in a simple “tree” design, that is totally collapsible and can easy be added to or “trimmed” with a click of a button.  It was meant to be logical and easy to follow. Integrated Contextual Help This is a fancy way of saying that you can practically yell “help!” if you do get stuck on something.  Solving a problem is as simple as highlighting and hitting F1 for contextual help. Visual Indicators and Messages Wouldn’t it be nice to know exactly where something has gone wrong before trying to complete a project.  expressor Studio has a built in system to catch mistakes and highlight them in a bright color, flash a warning message, and even disable functions before you can continue – and possibly lose hours of work. Property Inputs and Selectors Every operator will have a list of requirements that need to be filled in.  But don’t worry; you won’t have to make stuff up to fill in the boxes.  Each one will have a drop-down menu with options to choose from – but not too many as to be confusing. Connection Wizards Configuring connections can be the hardest part of a project.  But not with the expressor Studioconnection wizard.  A familiar, Windows-style menu will walk you through connections so quickly you’ll forget what trouble it used to be. Templates With large, complex projects, a majority of your time is often spent simply setting up the files and inputting data.  But expressor Studio allows you to create one file and then save it as a template, saving you hours of boring data input. Extension Manager Let’s say that you need a little more functionality or some new features on your program. A lot of software requires you to download complex plug-ins that need to be decompressed and installed.  However, expressor Studio has extended its system to an Extension Manager, which allows for quick and easy installation of the functionality you need, without the need to download and decompress. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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• SQL SERVER – Free Print Book on SQL Server Joes 2 Pros Kit

  - by pinaldave

  Rick Morelan and I were discussing earlier this month that what we can give back to the community. We believe our books are very much successful and very well received by the community. The five books are a journey from novice to expert. The books have changed many lives and helped many get jobs as well pass the SQL Certifications. Rick is from Seattle, USA and I am from Bangalore, India. There are 12 hours difference between us. We try to do weekly meeting to catch up on various personal and SQL related topics. Here is one of our recent conversations. Rick and Pinal Pinal: Good Morning Rick! Rick: Good Morning…err… Good Evening to you – Pinal! Pinal: Hey Rick, did you read the recent email which I sent you – one of our reader is thanking us for writing Joes 2 Pros series. He wants to dedicate his success to us. Can you believe it? Rick: Yeah, he is very kind but did you tell him that it is all because of his hard work on learning subject and we have very little contribution in his success. Pinal: Absolutely, I told him the same – I said we just wrote the book but it is he who learned from it and proved himself in his job. It is all him! We were just igniters. Rick: Good response. Pinal: Hey Rick! Are we doing enough for the community? What can we do more? Rick: Hmmm… Let us do something more. Pinal: Remember once we discussed the idea of if anyone who buys our Joes 2 Pros Combo Kit in the next 2 weeks – we will send them SQL Wait Stats for free. What do you say? Rick: I agree! Great Idea! Let us do it. Free Giveaway Well Rick and I liked the idea of doing more. We have decided to give away free SQL Server Wait Stats books to everybody who will purchase Joes 2 Pros Combo Kit between today (Oct 15, 2012) and Oct 26, 2012. This is not a contest or a lucky winner opportunity. Everybody who participates will qualify for it. Combo Availability USA – Amazon India - Flipkart | Indiaplaza Note1: USA kit contains FREE 5 DVDs. India Kit does not contain 5 DVDs due to legal issues. Note2: Indian Kit is priced at special Indian Economic Price. Qualify for Free Giveaway You must have purchased our Joes 2 Pros Combo Kit of 5 books between Oct 15, 2012 and Oct 26, 2012. Purchase before Oct 15, 2012 and after Oct 26, 2012 will not qualify for this giveaway. Send your original receipt (email, order details) to following addresses: “[email protected];[email protected]” with the subject line “Joes 2 Pros Kit Promotion Free Offer”. Do not change the subject line or your email may be missed.  Clearly mention your shipping address with phone number and pin/zip code. Send your receipt before Oct 30, 2012. We will not entertain any conversation after Oct 30, 2012 cut off date. The Free books will be sent to USA and India address only. Availability USA - Amazon | India - Flipkart | Indiaplaza Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, SQLServer, T SQL, Technology

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• SQL Server – SafePeak “Logon Trigger” Feature for Managing Data Access

  - by pinaldave

  Lately I received an interesting question about the abilities of SafePeak for SQL Server acceleration software: Q: “I would like to use SafePeak to make my CRM application faster. It is an application we bought from some vendor, after a while it became slow and we can’t reprogram it. SafePeak automated caching sounds like an easy and good solution for us. But, in my application there are many servers and different other applications services that address its main database, and some even change data, and I feel that there is a chance that some servers that during the connection process we may miss some. Is there a way to ensure that SafePeak will be aware of all connections to the SQL Server, so its cache will remain intact?” Interesting question, as I remember that SafePeak (http://www.safepeak.com/Product/SafePeak-Overview) likes that all traffic to the database will go thru it. I decided to check out the features of SafePeak latest version (2.1) and seek for an answer there. A: Indeed I found SafePeak has a feature they call “Logon Trigger” and is designed for that purpose. It is located in the user interface, under: Settings -> SQL instances management  ->  [your instance]  ->  [Logon Trigger] tab. From here you activate / deactivate it and control a white-list of enabled server IPs and Login names that SafePeak will ignore them. Click to Enlarge After activation of the “logon trigger” Safepeak server is notified by the SQL Server itself on each new opened connection. Safepeak monitors those connections and decides if there is something to do with them or not. On a typical installation SafePeak likes all application and users connections to go via SafePeak – this way it knows about data and schema updates immediately (real time). With activation of the safepeak “logon trigger”  a special CLR trigger is deployed on the SQL server and notifies Safepeak on any connection that has not arrived via SafePeak. In such cases Safepeak can act to clear and lock the cache or to ignore it. This feature enables to make sure SafePeak will be aware of all connections so SafePeak cache will maintain exactly correct all times. So even if a user, like a DBA will connect to the SQL Server not via SafePeak, SafePeak will know about it and take actions. The notification does not impact the work of that connection, the user or application still continue to do whatever they planned to do. Note: I found that activation of logon trigger in SafePeak requires that SafePeak SQL login will have the next permissions: 1) CONTROL SERVER; 2) VIEW SERVER STATE; 3) And the SQL Server instance is CLR enabled; Seeing SafePeak in action, I can say SafePeak brings fantastic resource for those who seek to get performance for SQL Server critical apps. SafePeak promises to accelerate SQL Server applications in just several hours of installation, automatic learning and some optimization configuration (no code changes!!!). If better application and database performance means better business to you – I suggest you to download and try SafePeak. The solution of SafePeak is indeed unique, and the questions I receive are very interesting. Have any more questions on SafePeak? Please leave your question as a comment and I will try to get an answer for you. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Puzzle – Statistics are not Updated but are Created Once

  - by pinaldave

  After having excellent response to my quiz – Why SELECT * throws an error but SELECT COUNT(*) does not?I have decided to ask another puzzling question to all of you. I am running this test on SQL Server 2008 R2. Here is the quick scenario about my setup. Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated Note: Auto Update Statistics and Auto Create Statistics for database is TRUE Expected Result – Statistics should be updated – SQL SERVER – When are Statistics Updated – What triggers Statistics to Update Now the question is why the statistics are not updated? The common answer is – we can update the statistics ourselves using UPDATE STATISTICS TableName WITH FULLSCAN, ALL However, the solution I am looking is where statistics should be updated automatically based on algorithm mentioned here. Now the solution is to ____________________. Vinod Kumar is not allowed to take participate over here as he is the one who has helped me to build this puzzle. I will publish the solution on next week. Please leave a comment and if your comment consist valid answer, I will publish with due credit. Here is the script to reproduce the scenario which I mentioned. -- Execution Plans Difference -- Create Sample Database CREATE DATABASE SampleDB GO USE SampleDB GO -- Create Table CREATE TABLE ExecTable (ID INT, FirstName VARCHAR(100), LastName VARCHAR(100), City VARCHAR(100)) GO -- Insert One Thousand Records -- INSERT 1 INSERT INTO ExecTable (ID,FirstName,LastName,City) SELECT TOP 1000 ROW_NUMBER() OVER (ORDER BY a.name) RowID, 'Bob', CASE WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%2 = 1 THEN 'Smith' ELSE 'Brown' END, CASE WHEN ROW_NUMBER() OVER (ORDER BY a.name)%20 = 1 THEN 'New York' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 5 THEN 'San Marino' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 3 THEN 'Los Angeles' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 7 THEN 'La Cinega' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 13 THEN 'San Diego' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 17 THEN 'Las Vegas' ELSE 'Houston' END FROM sys.all_objects a CROSS JOIN sys.all_objects b GO -- Display statistics of the table - none listed sp_helpstats N'ExecTable', 'ALL' GO -- Select Statement SELECT FirstName, LastName, City FROM ExecTable WHERE City  = 'New York' GO -- Display statistics of the table sp_helpstats N'ExecTable', 'ALL' GO -- Replace your Statistics over here -- NOTE: Replace your _WA_Sys with stats from above query DBCC SHOW_STATISTICS('ExecTable', _WA_Sys_00000004_7D78A4E7); GO -------------------------------------------------------------- -- Round 2 -- Insert Ten Thousand Records -- INSERT 2 INSERT INTO ExecTable (ID,FirstName,LastName,City) SELECT TOP 10000 ROW_NUMBER() OVER (ORDER BY a.name) RowID, 'Bob', CASE WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%2 = 1 THEN 'Smith' ELSE 'Brown' END, CASE WHEN ROW_NUMBER() OVER (ORDER BY a.name)%20 = 1 THEN 'New York' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 5 THEN 'San Marino' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 3 THEN 'Los Angeles' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 7 THEN 'La Cinega' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 13 THEN 'San Diego' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 17 THEN 'Las Vegas' ELSE 'Houston' END FROM sys.all_objects a CROSS JOIN sys.all_objects b GO -- Select Statement SELECT FirstName, LastName, City FROM ExecTable WHERE City  = 'New York' GO -- Display statistics of the table sp_helpstats N'ExecTable', 'ALL' GO -- Replace your Statistics over here -- NOTE: Replace your _WA_Sys with stats from above query DBCC SHOW_STATISTICS('ExecTable', _WA_Sys_00000004_7D78A4E7); GO -- You will notice that Statistics are still updated with 1000 rows -- Clean up Database DROP TABLE ExecTable GO USE MASTER GO ALTER DATABASE SampleDB SET SINGLE_USER WITH ROLLBACK IMMEDIATE; GO DROP DATABASE SampleDB GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Statistics, Statistics

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• SQL – Quick Start with Admin Sections of NuoDB – Manage NuoDB Database

  - by Pinal Dave

  In the yesterday’s blog post we have seen that it is extremely easy to install the NuoDB database on your local machine. Now that the application is properly set up, let us explore NuoDB a bit more and get you familiar with the how it works and what the important areas of the NuoDB are that you should learn. As we have already installed NuoDB, now we will quickly start with two of the important areas in NuoDB: 1) Admin and 2) Explorer. In this blog post I will explore how the Admin Section of the NuoDB Console works.  In the next blog post we will learn how the Explorer Section works. Let us go to the NuoDB Console by typing the following URL in your browser: http://localhost:8080/ It will bring you to the following screen: On this screen you can see a big Start QuickStart button. Click on the button and it will bring you to following screen. On this screen you will find very important information about Domain and Database Settings. It is our habit that we do not read what is written on the screen and keep on clicking on continue without reading. While we are familiar with most wizards, we can often miss the very important message on the screen. Please note the information of Domain Settings and Database Settings from the following screen before clicking on Create Database. Domain Settings User: quickstart Password: quickstart Database Settings User: dba Password: goalie Database: test Schema: HOCKEY Once you click on the Create Database button it will immediately start creating sample database. First, it will start a Storage Manager and right after that it will start a Transaction Engine. Once the engine is up, it will Create a Schema and Sample Data. On the success of the creating the sample database it will show the following screen. Now is the time where we can explore the NuoDB Admin or NuoDB Explorer. If you click on Admin, it will first show following login screen. Enter for the username “domain” and for the password “bird”. Alternatively you can enter “quickstart”  twice for username and password.  It works as too. Once you enter into the Admin Section, on the left side you can see information about NuoDB and Admin Console and on the right side you can see the domain overview area. From this Administrative section you can do any of the following tasks: Create a view of the entire domain Add and remove databases Start and stop NuoDB Transaction Engines and Storage Managers Monitor transaction across all the NuoDB databases On the right side of the Admin Section we can see various information about a particular NuoDB domain. You can quickly view various alerts, find out information about the number of host machines that are provisioned for the domain, and see the number of databases and processes that are running in the domain. If you click on the “1 host” link you will be able to see various processes, CPU usage and other information. In the Processes Section you can see that there are two different types of processes. The first process (where you can see the floppy drive icon) represents a running Storage Manager process and the second process a running Transaction Engine process. You can click on the links for the Storage Manager and Transaction Engine to see further statistical details right down to the last byte of the data. There are various charts available for analysis as well. I think the product is quite mature and the user can add different monitor charts to the Admin section. Additionally, the Admin section is the place where you can create and manage new databases. I hope today’s tutorial gives you enough confidence that you can try out NuoDB and checkout various administrative activities with the database. I am personally impressed with their dashboard related to various counters. For more information about how the NuoDB architecture works and what a Storage Manager or Transaction Engine does, check out this short video with NuoDB CTO Seth Proctor:  In the next blog post, we will try out the Explorer section of NuoDB, which allows us to run SQL queries and write SQL code.  Meanwhile, I strongly suggest you download and install NuoDB and get yourself familiar with the product. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: NuoDB

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• SQL SERVER – MSQL_XP – Wait Type – Day 20 of 28

  - by pinaldave

  In this blog post, I am going to discuss something from my field experience. While consultation, I have seen various wait typed, but one of my customers who has been using SQL Server for all his operations had an interesting issue with a particular wait type. Our customer had more than 100+ SQL Server instances running and the whole server had MSSQL_XP wait type as the most number of wait types. While running sp_who2 and other diagnosis queries, I could not immediately figure out what the issue was because the query with that kind of wait type was nowhere to be found. After a day of research, I was relieved that the solution was very easy to figure out. Let us continue discussing this wait type. From Book On-Line: ?MSQL_XP occurs when a task is waiting for an extended stored procedure to end. SQL Server uses this wait state to detect potential MARS application deadlocks. The wait stops when the extended stored procedure call ends. MSQL_XP Explanation: This wait type is created because of the extended stored procedure. Extended Stored Procedures are executed within SQL Server; however, SQL Server has no control over them. Unless you know what the code for the extended stored procedure is and what it is doing, it is impossible to understand why this wait type is coming up. Reducing MSQL_XP wait: As discussed, it is hard to understand the Extended Stored Procedure if the code for it is not available. In the scenario described at the beginning of this post, our client was using third-party backup tool. The third-party backup tool was using Extended Stored Procedure. After we learned that this wait type was coming from the extended stored procedure of the backup tool they were using, we contacted the tech team of its vendor. The vendor admitted that the code was not optimal at some places, and within that day they had provided the patch. Once the updated version was installed, the issue on this wait type disappeared. As viewed in the wait statistics of all the 100+ SQL Server, there was no more MSSQL_XP wait type found. In simpler terms, you must first identify which Extended Stored Procedure is creating the wait type of MSSQL_XP and see if you can get in touch with the creator of the SP so you can help them optimize the code. If you have encountered this MSSQL_XP wait type, I encourage all of you to write how you managed it. Please do not mention the name of the vendor in your comment as I will not approve it. The focus of this blog post is to understand the wait types; not talk about others. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussion of Wait Stats in this blog is generic and varies from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – DQS Error – Cannot connect to server – A .NET Framework error occurred during execution of user-defined routine or aggregate “SetDataQualitySessions” – SetDataQualitySessionPhaseTwo

  - by pinaldave

  Earlier I wrote a blog post about how to install DQS in SQL Server 2012. Today I decided to write a second part of this series where I explain how to use DQS, however, as soon as I started the DQS client, I encountered an error that will not let me pass through and connect with DQS client. It was a bit strange to me as everything was functioning very well when I left it last time.  The error was very big but here are the first few words of it. Cannot connect to server. A .NET Framework error occurred during execution of user-defined routine or aggregate “SetDataQualitySessions”: System.Data.SqlClient.SqlException (0×80131904): A .NET Framework error occurred during execution of user-defined routine or aggregate “SetDataQualitySessionPhaseTwo”: The error continues – here is the quick screenshot of the error. As my initial attempts could not fix the error I decided to search online and I finally received a wonderful solution from Microsoft Site. The error has happened due to latest update I had installed on .NET Framework 4. There was a  mismatch between the Module Version IDs (MVIDs) of the SQL Common Language Runtime (SQLCLR) assemblies in the SQL Server 2012 database and the Global Assembly Cache (GAC). This mismatch was to be resolved for the DQS to work properly. The workaround is specified here in detail. Scroll to subtopic 4.23 Some .NET Framework 4 Updates Might Cause DQS to Fail. The script was very much straight forward. Here are the few things to not to miss while applying workaround. Make sure DQS client is properly closed The NETAssemblies is based on your OS. NETAssemblies for 64 bit machine – which is my machine is “c:\windows\Microsoft.NET\Framework64\v4.0.30319″. If you have Winodws installed on any other drive other than c:\windows do not forget to change that in the above path. Additionally if you have 32 bit version installed on c:\windows you should use path as ”c:\windows\Microsoft.NET\Framework\v4.0.30319″ Make sure that you execute the script specified in 4.23 sections in this article in the database DQS_MAIN. Do not run this in the master database as this will not fix your error. Do not forget to restart your SQL Services once above script has been executed. Once you open the client it will work this time. Here is the script which I have bit modified from original script. I strongly suggest that you use original script mentioned 4.23 sections. However, this one is customized my own machine. /* Original source: http://bit.ly/PXX4NE (Technet) Modifications: -- Added Database context -- Added environment variable @NETAssemblies -- Main script modified to use @NETAssemblies */ USE DQS_MAIN GO BEGIN -- Set your environment variable -- assumption - Windows is installed in c:\windows folder DECLARE @NETAssemblies NVARCHAR(200) -- For 64 bit uncomment following line SET @NETAssemblies = 'c:\windows\Microsoft.NET\Framework64\v4.0.30319\' -- For 32 bit uncomment following line -- SET @NETAssemblies = 'c:\windows\Microsoft.NET\Framework\v4.0.30319\' DECLARE @AssemblyName NVARCHAR(200), @RefreshCmd NVARCHAR(200), @ErrMsg NVARCHAR(200) DECLARE ASSEMBLY_CURSOR CURSOR FOR SELECT name AS NAME FROM sys.assemblies WHERE name NOT LIKE '%ssdqs%' AND name NOT LIKE '%microsoft.sqlserver.types%' AND name NOT LIKE '%practices%' AND name NOT LIKE '%office%' AND name NOT LIKE '%stdole%' AND name NOT LIKE '%Microsoft.Vbe.Interop%' OPEN ASSEMBLY_CURSOR FETCH NEXT FROM ASSEMBLY_CURSOR INTO @AssemblyName WHILE @@FETCH_STATUS = 0 BEGIN BEGIN TRY SET @RefreshCmd = 'ALTER ASSEMBLY [' + @AssemblyName + '] FROM ''' + @NETAssemblies + @AssemblyName + '.dll' + ''' WITH PERMISSION_SET = UNSAFE' EXEC sp_executesql @RefreshCmd PRINT 'Successfully upgraded assembly ''' + @AssemblyName + '''' END TRY BEGIN CATCH IF ERROR_NUMBER() != 6285 BEGIN SET @ErrMsg = ERROR_MESSAGE() PRINT 'Failed refreshing assembly ' + @AssemblyName + '. Error message: ' + @ErrMsg END END CATCH FETCH NEXT FROM ASSEMBLY_CURSOR INTO @AssemblyName END CLOSE ASSEMBLY_CURSOR DEALLOCATE ASSEMBLY_CURSOR END GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – How to Ignore Columnstore Index Usage in Query

  - by pinaldave

  Earlier I wrote about SQL SERVER – Fundamentals of Columnstore Index and very first question I received in email was as following. “We are using SQL Server 2012 CTP3 and so far so good. In our data warehouse solution we have created 1 non-clustered columnstore index on our large fact table. We have very unique situation but your article did not cover it. We are running few queries on our fact table which is working very efficiently but there is one query which earlier was running very fine but after creating this non-clustered columnstore index this query is running very slow. We dropped the columnstore index and suddenly this one query is running fast but other queries which were benefited by this columnstore index it is running slow. Any workaround in this situation?” In summary the question in simple words “How can we ignore using columnstore index in selective queries?” Very interesting question – you can use I can understand there may be the cases when columnstore index is not ideal and needs to be ignored the same. You can use the query hint IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX to ignore the columnstore index. SQL Server Engine will use any other index which is best after ignoring the columnstore index. Here is the quick script to prove the same. We will first create sample database and then create columnstore index on the same. Once columnstore index is created we will write simple query. This query will use columnstore index. We will then show the usage of the query hint. USE AdventureWorks GO -- Create New Table CREATE TABLE [dbo].[MySalesOrderDetail]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [LineTotal] [numeric](38, 6) NOT NULL, [rowguid] [uniqueidentifier] NOT NULL, [ModifiedDate] [datetime] NOT NULL ) ON [PRIMARY] GO -- Create clustered index CREATE CLUSTERED INDEX [CL_MySalesOrderDetail] ON [dbo].[MySalesOrderDetail] ( [SalesOrderDetailID]) GO -- Create Sample Data Table -- WARNING: This Query may run upto 2-10 minutes based on your systems resources INSERT INTO [dbo].[MySalesOrderDetail] SELECT S1.* FROM Sales.SalesOrderDetail S1 GO 100 -- Create ColumnStore Index CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_MySalesOrderDetail_ColumnStore] ON [MySalesOrderDetail] (UnitPrice, OrderQty, ProductID) GO Now we have created columnstore index so if we run following query it will use for sure the same index. -- Select Table with regular Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID GO We can specify Query Hint IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX as described in following query and it will not use columnstore index. -- Select Table with regular Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID OPTION (IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX) GO Let us clean up the database. -- Cleanup DROP INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] GO TRUNCATE TABLE dbo.MySalesOrderDetail GO DROP TABLE dbo.MySalesOrderDetail GO Again, make sure that you use hint sparingly and understanding the proper implication of the same. Make sure that you test it with and without hint and select the best option after review of your administrator. Here is the question for you – have you started to use SQL Server 2012 for your validation and development (not on production)? It will be interesting to know the answer. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Sends backups to a Network Folder, FTP Server, Dropbox, Google Drive or Amazon S3

  - by pinaldave

  Let me tell you about one of the most useful SQL tools that every DBA should use – it is SQLBackupAndFTP. I have been using this tool since 2009 – and it is the first program I install on a SQL server. Download a free version, 1 minute configuration and your daily backups are safe in the cloud. In summary, SQLBackupAndFTP Creates SQL Server database and file backups on schedule Compresses and encrypts the backups Sends backups to a network folder, FTP Server, Dropbox, Google Drive or Amazon S3 Sends email notifications of job’s success or failure SQLBackupAndFTP comes in Free and Paid versions (starting from $29) – see version comparison. Free version is fully functional for unlimited ad hoc backups or for scheduled backups of up to two databases – it will be sufficient for many small customers. What has impressed me from the beginning – is that I understood how it works and was able to configure the job from a single form (see Image 1 – Main form above) Connect to you SQL server and select databases to be backed up Click “Add backup destination” to configure where backups should go to (network, FTP Server, Dropbox, Google Drive or Amazon S3) Enter your email to receive email confirmations Set the time to start daily full backups (or go to Settings if you need Differential or  Transaction Log backups on a flexible schedule) Press “Run Now” button to test You can get to this form if you click “Settings” buttons in the “Schedule section”. Select what types of backups and how often you want to run them and you will see the scheduled backups in the “Estimated backup plan” list A detailed tutorial is available on the developer’s website. Along with SQLBackupAndFTP setup gives you the option to install “One-Click SQL Restore” (you can install it stand-alone too) – a basic tool for restoring just Full backups. However basic, you can drag-and-drop on it the zip file created by SQLBackupAndFTP, it unzips the BAK file if necessary, connects to the SQL server on the start, selects the right database, it is smart enough to restart the server to drop open connections if necessary – very handy for developers who need to restore databases often. You may ask why is this tool is better than maintenance tasks available in SQL Server? While maintenance tasks are easy to set up, SQLBackupAndFTP is still way easier and integrates solution for compression, encryption, FTP, cloud storage and email which make it superior to maintenance tasks in every aspect. On a flip side SQLBackupAndFTP is not the fanciest tool to manage backups or check their health. It only works reliably on local SQL Server instances. In other words it has to be installed on the SQL server itself. For remote servers it uses scripting which is less reliable. This limitations is actually inherent in SQL server itself as BACKUP DATABASE command  creates backup not on the client, but on the server itself. This tool is compatible with almost all the known SQL Server versions. It works with SQL Server 2008 (all versions) and many of the previous versions. It is especially useful for SQL Server Express 2005 and SQL Server Express 2008, as they lack built in tools for backup. I strongly recommend this tool to all the DBAs. They must absolutely try it as it is free and does exactly what it promises. You can download your free copy of the tool from here. Please share your experience about using this tool. I am eager to receive your feedback regarding this article. Reference: Pinal Dave (http://blog.SQLAuthority.com)   Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, SQLServer, T SQL, Technology

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• SQL SERVER – CXPACKET – Parallelism – Advanced Solution – Wait Type – Day 7 of 28

  - by pinaldave

  Earlier we discussed about the what is the common solution to solve the issue with CXPACKET wait time. Today I am going to talk about few of the other suggestions which can help to reduce the CXPACKET wait. If you are going to suggest that I should focus on MAXDOP and COST THRESHOLD – I totally agree. I have covered them in details in yesterday’s blog post. Today we are going to discuss few other way CXPACKET can be reduced. Potential Reasons: If data is heavily skewed, there are chances that query optimizer may estimate the correct amount of the data leading to assign fewer thread to query. This can easily lead to uneven workload on threads and may create CXPAKCET wait. While retrieving the data one of the thread face IO, Memory or CPU bottleneck and have to wait to get those resources to execute its tasks, may create CXPACKET wait as well. Data which is retrieved is on different speed IO Subsystem. (This is not common and hardly possible but there are chances). Higher fragmentations in some area of the table can lead less data per page. This may lead to CXPACKET wait. As I said the reasons here mentioned are not the major cause of the CXPACKET wait but any kind of scenario can create the probable wait time. Best Practices to Reduce CXPACKET wait: Refer earlier article regarding MAXDOP and Cost Threshold. De-fragmentation of Index can help as more data can be obtained per page. (Assuming close to 100 fill-factor) If data is on multiple files which are on multiple similar speed physical drive, the CXPACKET wait may reduce. Keep the statistics updated, as this will give better estimate to query optimizer when assigning threads and dividing the data among available threads. Updating statistics can significantly improve the strength of the query optimizer to render proper execution plan. This may overall affect the parallelism process in positive way. Bad Practice: In one of the recent consultancy project, when I was called in I noticed that one of the ‘experienced’ DBA noticed higher CXPACKET wait and to reduce them, he has increased the worker threads. The reality was increasing worker thread has lead to many other issues. With more number of the threads, more amount of memory was used leading memory pressure. As there were more threads CPU scheduler faced higher ‘Context Switching’ leading further degrading performance. When I explained all these to ‘experienced’ DBA he suggested that now we should reduce the number of threads. Not really! Lower number of the threads may create heavy stalling for parallel queries. I suggest NOT to touch the setting of number of the threads when dealing with CXPACKET wait. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest reading book on-line for further clarification. All the discussion of Wait Stats over here is generic and it varies by system to system. You are recommended to test this on development server before implementing to production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – #TechEdIn – Presenting Tomorrow on SQL Server Misconception and Resolution with Vinod Kumar at TechEd India 2012

  - by pinaldave

  I am excited AND nervous at the same time. I am going to present a very interesting topic tomorrow at an SQL Server track in India. This will be my fourth time presenting at TechEd India. So far, I have received so much feedback about this one session. It seems like every single person out there has their own wishes and requests. I am sure that it is going to very challenging experience to satisfy everyone who attends the event through my presentation. Surprise Element Here is the good news: I am going to co-present this session with Vinod Kumar, my long time friend and co-worker. We have known each other for almost four years now, but this is the very first time that we are going to present together on the big stage of TechEd.  When there are more than two presenters, the usual trick is to practice the session multiple times and know exactly what each other is going to present and talk about. However, there’s a catch – we decided to make it different this time and have shared nothing to each other regarding what exactly we are going to present. This makes everything extremely interesting as each of us will be as clueless as the audience when other person is going to talk. Action Item Here are a few of the action items for all of those who are going to attend this session. Vinod and I will be present at the venue 15 minutes before the session. Do come in early and talk with us. We would be glad to talk with you and see if either of us can accommodate your suggestion in our session. If we do, we will give a surprise gift for you. As discussed, this session is going to be a unique two-presenter session. You will have chance to take a side with one speaker and stump the other speaker. Come early to decide which speaker you want to cheer during the session. Quiz and Goodies By now, you must have figured out that this session is going to be an extremely interactive session. We need your support through your active participation. We will have some really brain-twisting quiz line up just for you. You will have to take part and win surprises from us! Trust me. If you get it right, we will give you something which can help you learn more! We will have a quiz on Twitter as well. We will ask a question in person and you will be able to participate on Twitter. 10 – Demos As I said, both of us do not know what each other is going to present, but there are few things which we know very well. We have 10 demos and 6 slides. I think this is going to be an exciting demo marathon. Trust me, you will love it and the taste of this session will be in your mouth till the next TechEd. Session Details Title: SQL Server Misconceptions and Resolution – A Practical Perspective (Add to Calendar) Abstract: “The earth is flat”! – An ancient common misconception, which has been proven incorrect as we progressed in modern times. In this session, we will see various database misconceptions prevailing and their resolutions with the aid of the demos. In this unique session, the audience will be a part of the conversation and resolution. Date and Time: March 21, 2012, 15:15 to 16:15 Location: Hotel Lalit Ashok - Kumara Krupa High Grounds, Bengaluru – 560001, Karnataka, India. Add to Calendar Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• SQL SERVER – Understanding XML – Contest Win Joes 2 Pros Combo (USD 198) – Day 5 of 5

  - by pinaldave

  August 2011 we ran a contest where every day we give away one book for an entire month. The contest had extreme success. Lots of people participated and lots of give away. I have received lots of questions if we are doing something similar this month. Absolutely, instead of running a contest a month long we are doing something more interesting. We are giving away USD 198 worth gift every day for this week. We are giving away Joes 2 Pros 5 Volumes (BOOK) SQL 2008 Development Certification Training Kit every day. One copy in India and One in USA. Total 2 of the giveaway (worth USD 198). All the gifts are sponsored from the Koenig Training Solution and Joes 2 Pros. The books are available here Amazon | Flipkart | Indiaplaza How to Win: Read the Question Read the Hints Answer the Quiz in Contact Form in following format Question Answer Name of the country (The contest is open for USA and India residents only) 2 Winners will be randomly selected announced on August 20th. Question of the Day: Is following XML a well formed XML Document? <?xml version=”1.0″?> <address> <firstname>Pinal</firstname> <lastname>Dave</lastname> <title>Founder</title> <company>SQLAuthority.com</company> </address> a) Yes b) No c) I do not know Query Hints: BIG HINT POST A common observation by people seeing an XML file for the first time is that it looks like just a bunch of data inside a text file. XML files are text-based documents, which makes them easy to read.  All of the data is literally spelled out in the document and relies on a just a few characters (<, >, =) to convey relationships and structure of the data.  XML files can be used by any commonly available text editor, like Notepad. Much like a book’s Table of Contents, your first glance at well-formed XML will tell you the subject matter of the data and its general structure. Hints appearing within the data help you to quickly identify the main theme (similar to book’s subject), its headers (similar to chapter titles or sections of a book), data elements (similar to a book’s characters or chief topics), and so forth. We’ll learn to recognize and use the structural “hints,” which are XML’s markup components (e.g., XML tags, root elements). The XML Raw and Auto modes are great for displaying data as all attributes or all elements – but not both at once. If you want your XML stream to have some of its data shown in attributes and some shown as elements, then you can use the XML Path mode. If you are using an XML Path stream, then by default all values will be shown as elements. However, it is possible to pick one or more elements to be shown with an attribute(s) as well. Additional Hints: I have previously discussed various concepts from SQL Server Joes 2 Pros Volume 5. SQL Joes 2 Pros Development Series – OpenXML Options SQL Joes 2 Pros Development Series – Preparing XML in Memory SQL Joes 2 Pros Development Series – Shredding XML SQL Joes 2 Pros Development Series – Using Root With Auto XML Mode SQL Joes 2 Pros Development Series – Using Root With Auto XML Mode SQL Joes 2 Pros Development Series – What is XML? SQL Joes 2 Pros Development Series – What is XML? – 2 Next Step: Answer the Quiz in Contact Form in following format Question - Answer Name of the country (The contest is open for USA and India) Bonus Winner Leave a comment with your favorite article from the “additional hints” section and you may be eligible for surprise gift. There is no country restriction for this Bonus Contest. Do mention why you liked it any particular blog post and I will announce the winner of the same along with the main contest. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Guest Post – Glenn Berry – Wait Type – Day 26 of 28

  - by pinaldave

  Glenn Berry works as a Database Architect at NewsGator Technologies in Denver, CO. He is a SQL Server MVP, and has a whole collection of Microsoft certifications, including MCITP, MCDBA, MCSE, MCSD, MCAD, and MCTS. He is also an Adjunct Faculty member at University College – University of Denver, where he has been teaching since 2000. He is one wonderful blogger and often blogs at here. I am big fan of the Dynamic Management Views (DMV) scripts of Glenn. His script are extremely popular and the reality is that he has inspired me to start this series with his famous DMV which I have mentioned in very first  wait stats blog post (I had forgot to request his permission to re-use the script but when asked later on his whole hearty approved it). Here is is his excellent blog post on this subject of wait stats: Analyzing cumulative wait stats in SQL Server 2005 and above has become a popular and effective technique for diagnosing performance issues and further focusing your troubleshooting and diagnostic  efforts.  Rather than just guessing about what resource(s) that SQL Server is waiting on, you can actually find out by running a relatively simple DMV query. Once you know what resources that SQL Server is spending the most time waiting on, you can run more specific queries that focus on that resource to get a better idea what is causing the problem. I do want to throw out a few caveats about using wait stats as a diagnostic tool. First, they are most useful when your SQL Server instance is experiencing performance problems. If your instance is running well, with no indication of any resource pressure from other sources, then you should not worry that much about what the top wait types are. SQL Server will always be waiting on some resource, but many wait types are quite benign, and can be safely ignored. In spite of this, I quite often see experienced DBAs obsessing over the top wait type, even when their SQL Server instance is running extremely well. Second, I often see DBAs jump to the wrong conclusion based on seeing a particular well-known wait type. A good example is CXPACKET waits. People typically jump to the conclusion that high CXPACKET waits means that they should immediately change their instance-level MADOP setting to 1. This is not always the best solution. You need to consider your workload type, and look carefully for any important “missing” indexes that might be causing the query optimizer to use a parallel plan to compensate for the missing index. In this case, correcting the index problem is usually a better solution than changing MAXDOP, since you are curing the disease rather than just treating the symptom. Finally, you should get in the habit of clearing out your cumulative wait stats with the  DBCC SQLPERF(‘sys.dm_os_wait_stats’, CLEAR); command. This is especially important if you have made an configuration or index changes, or if your workload has changed recently. Otherwise, your cumulative wait stats will be polluted with the old stats from weeks or months ago (since the last time SQL Server was started or the stats were cleared).  If you make a change to your SQL Server instance, or add an index, you should clear out your wait stats, and then wait a while to see what your new top wait stats are. At any rate, enjoy Pinal Dave’s series on Wait Stats. This blog post has been written by Glenn Berry (Twitter | Blog) Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Solution of Puzzle – Swap Value of Column Without Case Statement

  - by pinaldave

  Earlier this week I asked a question where I asked how to Swap Values of the column without using CASE Statement. Read here: SQL SERVER – A Puzzle – Swap Value of Column Without Case Statement. I have proposed 3 different solutions in the blog posts itself. I had requested the help of the community to come up with alternate solutions and honestly I am stunned and amazed by the qualified entries. I will be not able to cover every single solution which is posted as a comment, however, I would like to for sure cover few interesting entries. However, I am selecting 5 solutions which are different (not necessary they are most optimal or best – just different and interesting). Just for clarity I am involving the original problem statement here. USE tempdb GO CREATE TABLE SimpleTable (ID INT, Gender VARCHAR(10)) GO INSERT INTO SimpleTable (ID, Gender) SELECT 1, 'female' UNION ALL SELECT 2, 'male' UNION ALL SELECT 3, 'male' GO SELECT * FROM SimpleTable GO -- Insert Your Solutions here -- Swap value of Column Gender SELECT * FROM SimpleTable GO DROP TABLE SimpleTable GO Here are the five most interesting and different solutions I have received. Solution by Roji P Thomas UPDATE S SET S.Gender = D.Gender FROM SimpleTable S INNER JOIN SimpleTable D ON S.Gender != D.Gender I really loved the solutions as it is very simple and drives the point home – elegant and will work pretty much for any values (not necessarily restricted by the option in original question ‘male’ or ‘female’). Solution by Aneel CREATE TABLE #temp(id INT, datacolumn CHAR(4)) INSERT INTO #temp VALUES(1,'gent'),(2,'lady'),(3,'lady') DECLARE @value1 CHAR(4), @value2 CHAR(4) SET @value1 = 'lady' SET @value2 = 'gent' UPDATE #temp SET datacolumn = REPLACE(@value1 + @value2,datacolumn,'') Aneel has very interesting solution where he combined both the values and replace the original value. I personally liked this creativity of the solution. Solution by SIJIN KUMAR V P UPDATE SimpleTable SET Gender = RIGHT(('fe'+Gender), DIFFERENCE((Gender),SOUNDEX(Gender))*2) Sijin has amazed me with Difference and Soundex function. I have never visualized that above two functions can resolve the problem. Hats off to you Sijin. Solution by Nikhildas UPDATE St SET St.Gender = t.Gender FROM SimpleTable St CROSS Apply (SELECT DISTINCT gender FROM SimpleTable WHERE St.Gender != Gender) t I was expecting that someone will come up with this solution where they use CROSS APPLY. This is indeed very neat and for sure interesting exercise. If you do not know how CROSS APPLY works this is the time to learn. Solution by mistermagooo UPDATE SimpleTable SET Gender=X.NewGender FROM (VALUES('male','female'),('female','male')) AS X(OldGender,NewGender) WHERE SimpleTable.Gender=X.OldGender As per author this is a slow solution but I love how syntaxes are placed and used here. I love how he used syntax here. I will say this is the most beautifully written solution (not necessarily it is best). Bonus: Solution by Madhivanan Somehow I was confident Madhi – SQL Server MVP will come up with something which I will be compelled to read. He has written a complete blog post on this subject and I encourage all of you to go ahead and read it. Now personally I wanted to list every single comment here. There are some so good that I am just amazed with the creativity. I will write a part of this blog post in future. However, here is the challenge for you. Challenge: Go over 50+ various solutions listed to the simple problem here. Here are my two asks for you. 1) Pick your best solution and list here in the comment. This exercise will for sure teach us one or two things. 2) Write your own solution which is yet not covered already listed 50 solutions. I am confident that there is no end to creativity. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Fix: Error : 402 The data types ntext and varchar are incompatible in the equal to operator

  - by pinaldave

  Some errors are very simple to understand but the solution of the same is not easy to figure out. Here is one of the similar errors where it clearly suggests where the problem is but does not tell what is the solution. Additionally, there are multiple solutions so developers often get confused with which one is correct and which one is not correct. Let us first recreate scenario and understand where the problem is. Let us run following USE Tempdb GO CREATE TABLE TestTable (ID INT, MyText NTEXT) GO SELECT ID, MyText FROM TestTable WHERE MyText = 'AnyText' GO DROP TABLE TestTable GO When you run above script it will give you following error. Msg 402, Level 16, State 1, Line 1 The data types ntext and varchar are incompatible in the equal to operator. One of the questions I often receive is that voucher is for sure compatible to equal to operator, then why does this error show up. Well, the answer is much simpler I think we have not understood the error message properly. Please see the image below. The next and varchar are not compatible when compared with each other using equal sign. Now let us change the data type on the right side of the string to nvarchar from varchar. To do that we will put N’ before the string. USE Tempdb GO CREATE TABLE TestTable (ID INT, MyText NTEXT) GO SELECT ID, MyText FROM TestTable WHERE MyText = N'AnyText' GO DROP TABLE TestTable GO When you run above script it will give following error. Msg 402, Level 16, State 1, Line 1 The data types ntext and nvarchar are incompatible in the equal to operator. You can see that error message also suggests that now we are comparing next to nvarchar. Now as we have understood the error properly, let us see various solutions to the above problem. Solution 1: Convert the data types to match with each other using CONVERT function. Change the datatype of the MyText to nvarchar. SELECT ID, MyText FROM TestTable WHERE CONVERT(NVARCHAR(MAX), MyText) = N'AnyText' GO Solution 2: Convert the data type of columns from NTEXT to NVARCHAR(MAX) (TEXT to VARCHAR(MAX) ALTER TABLE TestTable ALTER COLUMN MyText NVARCHAR(MAX) GO Now you can run the original query again and it will work fine. Solution 3: Using LIKE command instead of Equal to command. SELECT ID, MyText FROM TestTable WHERE MyText LIKE 'AnyText' GO Well, any of the three of the solutions will work. Here is my suggestion if you can change the column data type from ntext or text to nvarchar or varchar, you should follow that path as text and ntext datatypes are marked as deprecated. All developers any way to change the deprecated data types in future, it will be a good idea to change them right early. If due to any reason you can not convert the original column use Solution 1 for temporary fix. Solution 3 is the not the best solution and use it as a last option. Did I miss any other method? If yes, please let me know and I will add the solution to original blog post with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQLAuthority News – Follow up on – Replace a Column Name in Multiple Stored Procedure all together

  - by pinaldave

  Last month I had a fantastic time with lots of puzzles and brain teasers, the amount of participation which I have received on the blog is indeed inspiring to write more. One of the blog post was about how to replace a column name in all the stored procedures. The article had very interesting conversation as a follow up. Please read the original article Replace a Column Name in Multiple Stored Procedure all together before reading this blog further as they are connected. Let us start few of the interesting comments. SQL Server Expert Imran Mohammed had a wonderful first and excellent note. I suggest all of you to read it. Imran stresses on the Data Modelling and Logical as well as Physical Design. Developers must create a logical design and get approval on naming convention, data types, references, constraints, indexes etc. He further suggested that one should not cut steps but must follow all the industry standards and guidelines. Here extended my blog post with following note – “Extending Pinal’s answer, what you can do is go to database properties, all tasks, scripts objects, in scripting wizard select all the stored procedure for which you want to change column name, export the query to a new window and then do find and replace, all in once window and execute the script. But make sure you check what you are replacing, sometimes column names are also used in table names, for ex:Table Name: Product and Column Name: ProductId, ProductName”. Thanks Imran Great Points!  Gatej Alexandru suggested that it is not good idea to DROP or CREATE but rather use ALTER as quite possible there may be permissions issue as well. Very good point let me see if I can write blog post over it. Vinay Kumar and SQLStudent144 have proposed another method to achieve the same. I am combining their solution and writing them here. Step 1. Press Ctrl+T or change “Result to Text” mode. Step 2. Execute below commands.SELECT 'EXEC sp_helptext [' + referencing_schema_name + '.' + referencing_entity_name + ']' FROM sys.dm_sql_referencing_entities('schema.objectname','OBJECT') Where schema.objectname is the object or table you are searching for. Step 3. Now copy the result and paste in new window. Again Press Ctrl+T or change “Result to Text” mode. Step 4. Copy the result and paste in new window. Execute the query. Step 5. Copy the result and paste in new window. Step 6. Now find your searching text in the script, make necessary changes and execute this script. Do not forget to remove the code which is generated in resultset which are not relevant to the T-SQL Script. Digitqr suggest we can do this for other objects besides Stored Procedure as well. Iosif suggests to use tool SQL Search from RedGate. I guess this sums it well. We have an alternative perspective to our original issue of replacing the column name in multiple stored procedure. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – master Database Log File Grew Too Big

  - by pinaldave

  Couple of the days ago, I received following email and I find this email very interesting and I feel like sharing with all of you. Note: Please read the whole email before providing your suggestions. “Hi Pinal, If you can share these details on your blog, it will help many. We understand the value of the master database and we take its regular back up (everyday midnight). Yesterday we noticed that our master database log file has grown very large. This is very first time that we have encountered such an issue. The master database is in simple recovery mode; so we assumed that it will never grow big; however, we now have a big log file. We ran the following command USE [master] GO DBCC SHRINKFILE (N'mastlog' , 0, TRUNCATEONLY) GO We know this command will break the chains of LSN but as per our understanding; it should not matter as we are in simple recovery model.     After running this, the log file becomes very small. Just to be cautious, we took full backup of the master database right away. We totally understand that this is not the normal practice; so if you are going to tell us the same, we are aware of it. However, here is the question for you? What operation in master database would have caused our log file to grow too large? Thanks, [name and company name removed as per request]“ Here was my response to them: “Hi [name removed], It is great that you are aware of all the right steps and method. Taking full backup when you are not sure is always a good practice. Regarding your question what could have caused your master database log to grow larger, let me try to guess what could have happened. Do you have any user table in the master database? If yes, this is not recommended and also NOT a good practice. If have user tables in master database and you are doing any long operation (may be lots of insert, update, delete or rebuilding them), then it can cause this situation. You have made me curious about your scenario; do revert back. Kind Regards, Pinal” Within few minutes I received reply: “That was it Pinal. We had one of the maintenance task log tables created in the master table, which had many long transactions during the night. We moved it to newly created database named ‘maintenance’, and we will keep you updated.” I was very glad to receive the email. I do not suggest that any user table should be created in the master database. It should be left alone from user objects. Now here is the question for you – can you think of any other reason for master log file growth? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – A Puzzle – Swap Value of Column Without Case Statement

  - by pinaldave

  For the last few weeks, I have been doing Friday Puzzles and I am really loving it. Yesterday I received a very interesting question by Navneet Chaurasia on Facebook Page. He was asked this question in one of the interview questions for job. Please read the original thread for a complete idea of the conversation. I am presenting the same question here. Puzzle Let us assume there is a single column in the table called Gender. The challenge is to write a single update statement which will flip or swap the value in the column. For example if the value in the gender column is ‘male’ swap it with ‘female’ and if the value is ‘female’ swap it with ‘male’. Here is the quick setup script for the puzzle. USE tempdb GO CREATE TABLE SimpleTable (ID INT, Gender VARCHAR(10)) GO INSERT INTO SimpleTable (ID, Gender) SELECT 1, 'female' UNION ALL SELECT 2, 'male' UNION ALL SELECT 3, 'male' GO SELECT * FROM SimpleTable GO The above query will return following result set. The puzzle was to write a single update column which will generate following result set. There are multiple answers to this simple puzzle. Let me show you three different ways. I am assuming that the column will have either value ‘male’ or ‘female’ only. Method 1: Using CASE Statement I believe this is going to be the most popular solution as we are all familiar with CASE Statement. UPDATE SimpleTable SET Gender = CASE Gender WHEN 'male' THEN 'female' ELSE 'male' END GO SELECT * FROM SimpleTable GO Method 2: Using REPLACE  Function I totally understand it is the not cleanest solution but it will for sure work in giving situation. UPDATE SimpleTable SET Gender = REPLACE(('fe'+Gender),'fefe','') GO SELECT * FROM SimpleTable GO Method 3: Using IIF in SQL Server 2012 If you are using SQL Server 2012 you can use IIF and get the same effect as CASE statement. UPDATE SimpleTable SET Gender = IIF(Gender = 'male', 'female', 'male') GO SELECT * FROM SimpleTable GO You can read my article series on SQL Server 2012 various functions over here. SQL SERVER – Denali – Logical Function – IIF() – A Quick Introduction SQL SERVER – Detecting Leap Year in T-SQL using SQL Server 2012 – IIF, EOMONTH and CONCAT Function Let us clean up. DROP TABLE SimpleTable GO Question to you: I came up with three simple tricks where there is a single UPDATE statement which swaps the values in the column. Do you know any other simple trick? If yes, please post here in the comments. I will pick two random winners from all the valid answers. Winners will get 1) Print Copy of SQL Server Interview Questions and Answers 2) Free Learning Code for Online Video Courses I will announce the winners on coming Monday. Reference:  Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• SQL SERVER – Discard Results After Query Execution – SSMS

  - by pinaldave

  The first thing I do any day is to turn on the computer. Today I woke up and as soon as I turned on the computer I saw a chat message from a friend. He was a bit confused and wanted me to help him. Just as usual I am keeping the relevant conversation in focus and documenting our conversation as chat. Let us call him Ajit. Ajit: Pinal, every time I run a query there is no result displayed in the SSMS but when I run the query in my application it works and returns an appropriate result. Pinal:  Have you tried with different parameters? Ajit: Same thing. However, it works from another computer when I connect to the same server with the same query parameters? Pinal: What? That is new and I believe it is something to do with SSMS and not with the server. Send me screenshot please. Ajit: I believe so, let me send you a screenshot, Pinal: (looking at the screenshot) Oh man, there is no result-tab at all. Ajit: That is what the problem is. It does not have the tab which displays the result. This works just fine from another computer. Pinal: Have you referred Nakul’s blog post – SSMS – Query result options – Discard result after query executes, that talks about setting which can discard the query results after execution. (After a while) Ajit: I think it seems like on the computer where I am running the query my SSMS seems to have the option enabled related to discarding results. I fixed it by following Nakul’s blog post. Pinal: Great! Quite often I get the question what is the importance of the feature. Let us first see how to turn on or turn off this feature in SQL Server Management Studio 2012. In SSMS 2012 go to Tools >> Options >> Query Results > SQL Server >> Results to Grid >> Discard Results After Query Execution. When enabled this option will discard results after the execution. The advantage of disabling the option is that it will improve the performance by using less memory. However the real question is why would someone enable or disable the option. What are the cases when someone wants to run the query but do not care about the result? Matter of the fact, it does not make sense at all to run query and not care about the result. The matter of the fact, I can see quite a few reasons for using this option. I often enable this option when I am doing performance tuning exercise. During performance tuning exercise when I am working with execution plans and do not need results to verify every time or when I am tuning Indexes and its effect on execution plan I do not need the results. In this kind of situations I do keep this option on and discard the results. It always helps me big time as in most of the performance tuning exercise I am dealing with huge amount of the data and dealing with this data can be expensive. Nakul’s has done the experiment here already but I am going to repeat the same again using AdventureWorks Database. Run following T-SQL Script with and without enabling the option to discard the results. USE AdventureWorks2012 GO SELECT * FROM Sales.SalesOrderDetail GO 10 After enabling Discard Results After Query Execution After disabling Discard Results After Query Execution Well, this is indeed a good option when someone is debugging the execution plan or does not want the result to be displayed. Please note that this option does not reduce IO or CPU usage for SQL Server. It just discards the results after execution and a good help for debugging on the development server. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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• SQLAuthority News – Book Signing Event – SQLPASS 2011 Event Log

  - by pinaldave

  I have been dreaming of writing book for really long time, and I finally got the chance – in fact, two chances!  I recently wrote two books: SQL Programming Joes 2 Pros: Programming and Development for Microsoft SQL Server 2008 [Amazon] | [Flipkart] | [Kindle] and SQL Wait Stats Joes 2 Pros: SQL Performance Tuning Techniques Using Wait Statistics, Types & Queues [Amazon] | [Flipkart] | [Kindle].  I had a lot of fun writing these two books, even though sometimes I had to sacrifice some family time and time for other personal development to write the books. The good side of writing book is that when the efforts put in writing books are recognize by books readers and kind organizations like expressor studio. Book Signing Event Book writing is a complex process.  Even after you spend months, maybe years, writing the material you still have to go through the editing and fact checking processes.  And, once the book is out there, there is no way to take back all the copies to change mistakes or add something you forgot.  Most of the time it is a one-way street. Book Signing Event Just like every author, I had a dream that after the books were written, they would be loved by people and gain acceptance by an audience. My first book, SQL Programming Joes 2 Pros: Programming and Development for Microsoft SQL Server 2008, is extremely popular because it helps lots of people learn various fundamental topics. My second book covers beginning to learn SQL Server Wait Stats, which is a relatively new subject. This book has had very good acceptance in the community. Book Signing Event Helping my community is my primary focus, so I was happy to see this year’s SQLPASS tag line: ‘This is a Community.‘ At the event, the expressor studio guys came up with a very novel idea. They had previously used my books and they had found them very useful. They got 100 copies of the book and decided to give it away to community folks. They invited me and my co-author Rick Morelan to hold a book signing event. We did a book signing on Thursday between 1 pm and 2 pm. Book Signing Event This event was one of the best events for me. This was my first book signing event outside of India. I reached the book signing location around 20 minutes before the scheduled time and what I saw was a big line for the book signing event. I felt very honored looking at the crowd and all the people around the event location. I felt very humbled when I saw some of my very close friends standing in the line to get my signature. It was really heartwarming to see so many enthusiasts waiting for more than an hour to get my signature. While standing in line I had the chance to have a conversation with every single person who showed up for the signature. I made sure that I repeated every single name and wrote it in every book with my signature. There is saying that if we write a name once we will remember it forever. I want to remember all of you who saw me at the book signing. Your comments were wonderful, your feedback was amazing and you were all very supportive. Book Signing Event I have made a note of every conversation I had with all of you when I was signing the books. Once again, I just want to express my thanks for coming to my book signing event. The whole experience was very humbling. On the top of it, I want to thank the expressor studio people who made it possible, who organized the whole signing event. I am so thankful to them for facilitating the whole experience, which is going to be hard to beat by any future experience. My books Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL PASS, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, T SQL, Technology

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• SQL SERVER – Identity Fields – Contest Win Joes 2 Pros Combo (USD 198) – Day 2 of 5

  - by pinaldave

  August 2011 we ran a contest where every day we give away one book for an entire month. The contest had extreme success. Lots of people participated and lots of give away. I have received lots of questions if we are doing something similar this month. Absolutely, instead of running a contest a month long we are doing something more interesting. We are giving away USD 198 worth gift every day for this week. We are giving away Joes 2 Pros 5 Volumes (BOOK) SQL 2008 Development Certification Training Kit every day. One copy in India and One in USA. Total 2 of the giveaway (worth USD 198). All the gifts are sponsored from the Koenig Training Solution and Joes 2 Pros. The books are available here Amazon | Flipkart | Indiaplaza How to Win: Read the Question Read the Hints Answer the Quiz in Contact Form in following format Question Answer Name of the country (The contest is open for USA and India residents only) 2 Winners will be randomly selected announced on August 20th. Question of the Day: Which of the following statement is incorrect? a) Identity value can be negative. b) Identity value can have negative interval. c) Identity value can be of datatype VARCHAR d) Identity value can have increment interval larger than 1 Query Hints: BIG HINT POST A simple way to determine if a table contains an identity field is to use the SSMS Object Explorer Design Interface. Navigate to the table, then right-click it and choose Design from the pop-up window. When your design tab opens, select the first field in the table to view its list of properties in the lower pane of the tab (In this case the field is ProductID). Look to see if the Identity Specification property in the lower pane is set to either yes or no. SQL Server will allow you to utilize IDENTITY_INSERT with just one table at a time. After you’ve completed the needed work, it’s very important to reset the IDENTITY_INSERT back to OFF. Additional Hints: I have previously discussed various concepts from SQL Server Joes 2 Pros Volume 2. SQL Joes 2 Pros Development Series – Output Clause in Simple Examples SQL Joes 2 Pros Development Series – Ranking Functions – Advanced NTILE in Detail SQL Joes 2 Pros Development Series – Ranking Functions – RANK( ), DENSE_RANK( ), and ROW_NUMBER( ) SQL Joes 2 Pros Development Series – Advanced Aggregates with the Over Clause SQL Joes 2 Pros Development Series – Aggregates with the Over Clause SQL Joes 2 Pros Development Series – Overriding Identity Fields – Tricks and Tips of Identity Fields SQL Joes 2 Pros Development Series – Many to Many Relationships Next Step: Answer the Quiz in Contact Form in following format Question Answer Name of the country (The contest is open for USA and India) Bonus Winner Leave a comment with your favorite article from the “additional hints” section and you may be eligible for surprise gift. There is no country restriction for this Bonus Contest. Do mention why you liked it any particular blog post and I will announce the winner of the same along with the main contest. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – ASYNC_IO_COMPLETION – Wait Type – Day 11 of 28

  - by pinaldave

  For any good system three things are vital: CPU, Memory and IO (disk). Among these three, IO is the most crucial factor of SQL Server. Looking at real-world cases, I do not see IT people upgrading CPU and Memory frequently. However, the disk is often upgraded for either improving the space, speed or throughput. Today we will look at another IO-related wait type. From Book On-Line: Occurs when a task is waiting for I/Os to finish. ASYNC_IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. If by any means your application that’s connected to SQL Server is processing the data very slowly, this type of wait can occur. Several long-running database operations like BACKUP, CREATE DATABASE, ALTER DATABASE or other operations can also create this wait type. Reducing ASYNC_IO_COMPLETION wait: When it is an issue related to IO, one should check for the following things associated to IO subsystem: Look at the programming and see if there is any application code which processes the data slowly (like inefficient loop, etc.). Note that it should be re-written to avoid this  wait type. Proper placing of the files is very important. We should check the file system for proper placement of the files – LDF and MDF on separate drive, TempDB on another separate drive, hot spot tables on separate filegroup (and on separate disk), etc. Check the File Statistics and see if there is a higher IO Read and IO Write Stall SQL SERVER – Get File Statistics Using fn_virtualfilestats. Check event log and error log for any errors or warnings related to IO. If you are using SAN (Storage Area Network), check the throughput of the SAN system as well as configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly and so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on the development setup (test environment). As soon as we changed the HBA Queue Depth to quite a higher value, there was a sudden big improvement in the performance. It is very likely to happen that there are no proper indexes on the system and yet there are lots of table scans and heap scans. Creating proper index can reduce the IO bandwidth considerably. If SQL Server can use appropriate cover index instead of clustered index, it can effectively reduce lots of CPU, Memory and IO (considering cover index has lesser columns than cluster table and all other; it depends upon the situation). You can refer to the following two articles I wrote that talk about how to optimize indexes: Create Missing Indexes Drop Unused Indexes Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Another lesser known feature of SQL Server Management Studio 2012 – Guest Post by Balmukund Lakhani

  - by Pinal Dave

  This is a fantastic blog post from my dear friend Balmukund ( blog | twitter | facebook ). He had presented a fantastic session in our last UG and there were lots of requests from attendees that he blogs about it. Well, here is the blog post about the same very popular UG session. Let us read the entire blog post in the voice of the Balmukund himself. In one of my previous guest blog on SQL Authority, I wrote about “Additional Connection Parameter” tab of login screen in SQL Server Management Studio (a.k.a. SSMS). On the similar lines, this blog is going to show little less known new feature of login main screen (“Connect to Server”) of SSMS 2012. You might have seen below screen countless times and you might wonder what is there is blog about in this simple screen. Well, continue reading and you would get the answer. Many times, DBA have to login to production server from non-regular machine, may be a developer’s workstation. Once you login to SQL, do your work and close the management studio. Do you know that your server name is saved in management studio? Of course, very useful feature because you may not like to type server name/IP address every time. Whatever servers you have connected, it would be stored by management studio. But sometime, it’s annoying! What you would do if you want SQL Server Management Studio to forget “all” the servers listed in drop down of Server name? To do that, you need to know how and where it’s stored. You can use one of my favorite tool from sysinternals called Process Monitor (also known as ProcMon) and easily figure out that this is stored in a file under your windows user profile. Below is the file in SQL 2008 R2 Management Studio. %appdata%\Microsoft\Microsoft SQL Server\100\Tools\Shell\SqlStudio.bin For SQL Server 2012, here is what we can see in ProcMon So, the path is %appdata%\Microsoft\Microsoft SQL Server\110\Tools\Shell\SqlStudio.bin So far, you might wonder, where is the new feature? I have been asked by many users to delete entries from SSMS “Connect to Server” server name list. Well, unofficially, you can delete the file directly which we found via ProcMon. Note that delete file to get rid of server list is not officially supported by Microsoft. Better way to achieve this is provided in SSMS 2012. To delete the servers from the list, highlight the name we want to delete (via keyboard or mouse) and then press delete key via keyboard. We can’t be multi-select and has to be done one by one. We can delete as many entries we want. I have delete few from first screenshot taken and here is the modified version. This is not available in SQL 2008 R2 and its previous version. This came from feedback given to SQL Server Product group. Hope you have learned something new today! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – IO_COMPLETION – Wait Type – Day 10 of 28

  - by pinaldave

  For any good system three things are vital: CPU, Memory and IO (disk). Among these three, IO is the most crucial factor of SQL Server. Looking at real-world cases, I do not see IT people upgrading CPU and Memory frequently. However, the disk is often upgraded for either improving the space, speed or throughput. Today we will look at an IO-related wait types. From Book On-Line: Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits. IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. This is a good indication that IO needs to be looked over here. Reducing IO_COMPLETION wait: When it is an issue concerning the IO, one should look at the following things related to IO subsystem: Proper placing of the files is very important. We should check the file system for proper placement of files – LDF and MDF on a separate drive, TempDB on another separate drive, hot spot tables on separate filegroup (and on separate disk),etc. Check the File Statistics and see if there is higher IO Read and IO Write Stall SQL SERVER – Get File Statistics Using fn_virtualfilestats. Check event log and error log for any errors or warnings related to IO. If you are using SAN (Storage Area Network), check the throughput of the SAN system as well as the configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on development (test environment) set up and as soon as we changed the HBA Queue Depth to quite a higher value, there was a sudden big improvement in the performance. It is very possible that there are no proper indexes in the system and there are lots of table scans and heap scans. Creating proper index can reduce the IO bandwidth considerably. If SQL Server can use appropriate cover index instead of clustered index, it can effectively reduce lots of CPU, Memory and IO (considering cover index has lesser columns than cluster table and all other; it depends upon the situation). You can refer to the two articles that I wrote; they are about how to optimize indexes: Create Missing Indexes Drop Unused Indexes Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Types, SQL White Papers, T SQL, Technology

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