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• SQL SERVER – Size of Index Table for Each Index – Solution 3 – Powershell

  - by pinaldave

  Laerte Junior If you are a Powershell user, the name of the Laerte Junior is not a new name. He is the one man with exceptional knowledge of Powershell. He is not only very knowledgeable, but also very kind and eager to those in need. I have been attempting to setup Powershell for many days, but constantly facing issues. I was not able to get going with this tool. Finally, yesterday I sent email to Laerte in response to his comment posted here. Within 5 minutes, Laerte came online and helped me with the solution. He spend nearly 15 minutes working along with me to solve my problem with installation. And yes, he did resolve it remotely without looking at my screen – What a skilled and exceptional person!! I will soon post a detail note about the issue I faced and resolved with the help of Laerte. Here is his solution to my earlier puzzle in his own words. Read the original puzzle here and Laerte’s solution from here. Hi Pinal, I do not say better, but maybe another approach to enthusiasts in powershell and SQLSPX library would be: 1 – All indexes in all tables and all databases Get-SqlDatabase -sqlserver “Yourserver” | Get-SqlTable | Get-SqlIndex | Format-table Server,dbname,schema,table,name,id,spaceused 2 – All Indexes in all tables and specific database Get-SqlDatabase -sqlserver “Yourserver” “Yourdb” | Get-SqlTable | Get-SqlIndex | Format-table Server,dbname,schema,table,name,id,spaceused 3 – All Indexes in specific table and database Get-SqlDatabase -sqlserver “Yourserver” “Yourdb” | Get-SqlTable “YourTable” | Get-SqlIndex | Format-table Server,dbname,schema,table,name,id,spaceused and to output to txt.. pipe Out-File Get-SqlDatabase -sqlserver “Yourserver” | Get-SqlTable | Get-SqlIndex | Format-table Server,dbname,schema,table,name,id,spaceused | out-file c:\IndexesSize.txt If you have one txt with all your servers, can be for all of them also. Lets say you have all your servers in servers.txt: something like NameServer1 NameServer2 NameServer3 NameServer4 We could Use : foreach ($Server in Get-content c:\temp\servers.txt) { Get-SqlDatabase -sqlserver $Server | Get-SqlTable | Get-SqlIndex | Format-table Server,dbname,schema,table,name,id,spaceused } :) After fixing my issue with Powershell, I ran Laerte‘s second suggestion – “All Indexes in all tables and specific database” and found the following accurate output. Click to Enlarge Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Index, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Powershell

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• SQL SERVER – Copy Data from One Table to Another Table – SQL in Sixty Seconds #031 – Video

  - by pinaldave

  Copy data from one table to another table is one of the most requested questions on forums, Facebook and Twitter. The question has come in many formats and there are places I have seen developers are using cursor instead of this direct method. Earlier I have written the similar article a few years ago - SQL SERVER – Insert Data From One Table to Another Table – INSERT INTO SELECT – SELECT INTO TABLE. The article has been very popular and I have received many interesting and constructive comments. However there were two specific comments keep on ending up on my mailbox. 1) SQL Server AdventureWorks Samples Database does not have table I used in the example 2) If there is a video tutorial of the same example. After carefully thinking I decided to build a new set of the scripts for the example which are very similar to the old one as well video tutorial of the same. There was no better place than our SQL in Sixty Second Series to cover this interesting small concept. Let me know what you think of this video. Here is the updated script. -- Method 1 : INSERT INTO SELECT USE AdventureWorks2012 GO ----Create TestTable CREATE TABLE TestTable (FirstName VARCHAR(100), LastName VARCHAR(100)) ----INSERT INTO TestTable using SELECT INSERT INTO TestTable (FirstName, LastName) SELECT FirstName, LastName FROM Person.Person WHERE EmailPromotion = 2 ----Verify that Data in TestTable SELECT FirstName, LastName FROM TestTable ----Clean Up Database DROP TABLE TestTable GO --------------------------------------------------------- --------------------------------------------------------- -- Method 2 : SELECT INTO USE AdventureWorks2012 GO ----Create new table and insert into table using SELECT INSERT SELECT FirstName, LastName INTO TestTable FROM Person.Person WHERE EmailPromotion = 2 ----Verify that Data in TestTable SELECT FirstName, LastName FROM TestTable ----Clean Up Database DROP TABLE TestTable GO Related Tips in SQL in Sixty Seconds: SQL SERVER – Insert Data From One Table to Another Table – INSERT INTO SELECT – SELECT INTO TABLE Powershell – Importing CSV File Into Database – Video SQL SERVER – 2005 – Export Data From SQL Server 2005 to Microsoft Excel Datasheet SQL SERVER – Import CSV File into Database Table Using SSIS SQL SERVER – Import CSV File Into SQL Server Using Bulk Insert – Load Comma Delimited File Into SQL Server SQL SERVER – 2005 – Generate Script with Data from Database – Database Publishing Wizard What would you like to see in the next SQL in Sixty Seconds video? Reference: Pinal Dave (http://blog.sqlauthority.com)   Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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• SQL SERVER – Understanding ALTER INDEX ALL REBUILD with Disabled Clustered Index

  - by pinaldave

  This blog is in response to the ongoing communication with the reader who had earlier asked the question of SQL SERVER – Disable Clustered Index and Data Insert. The same reader has asked me the difference between ALTER INDEX ALL REBUILD and ALTER INDEX REBUILD along with disabled clustered index. Instead of writing a big theory, we will go over the demo right away. Here are the steps that we intend to follow. 1) Create Clustered and Nonclustered Index 2) Disable Clustered and Nonclustered Index 3) Enable – a) All Indexes, b) Clustered Index USE tempdb GO -- Drop Table if Exists IF EXISTS (SELECT * FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[TableName]') AND type IN (N'U')) DROP TABLE [dbo].[TableName] GO -- Create Table CREATE TABLE [dbo].[TableName]( [ID] [int] NOT NULL, [FirstCol] [varchar](50) NULL ) GO -- Create Clustered Index ALTER TABLE [TableName] ADD CONSTRAINT [PK_TableName] PRIMARY KEY CLUSTERED ([ID] ASC) GO -- Create Nonclustered Index CREATE UNIQUE NONCLUSTERED INDEX [IX_NonClustered_TableName] ON [dbo].[TableName] ([FirstCol] ASC) GO -- Check that all the indexes are enabled SELECT OBJECT_NAME(OBJECT_ID), Name, type_desc, is_disabled FROM sys.indexes WHERE OBJECT_NAME(OBJECT_ID) = 'TableName' GO Now let us disable both the indexes. -- Disable Indexes -- Disable Nonclustered Index ALTER INDEX [IX_NonClustered_TableName] ON [dbo].[TableName] DISABLE GO -- Disable Clustered Index ALTER INDEX [PK_TableName] ON [dbo].[TableName] DISABLE GO -- Check that all the indexes are disabled SELECT OBJECT_NAME(OBJECT_ID), Name, type_desc, is_disabled FROM sys.indexes WHERE OBJECT_NAME(OBJECT_ID) = 'TableName' GO Next, let us rebuild all the indexes and see the output. -- Test 1: ALTER INDEX ALL REBUILD -- Rebuliding should work fine ALTER INDEX ALL ON [dbo].[TableName] REBUILD GO -- Check that all the indexes are enabled SELECT OBJECT_NAME(OBJECT_ID), Name, type_desc, is_disabled FROM sys.indexes WHERE OBJECT_NAME(OBJECT_ID) = 'TableName' GO Now, once again disable indexes for the second test. -- Disable Indexes -- Disable Nonclustered Index ALTER INDEX [IX_NonClustered_TableName] ON [dbo].[TableName] DISABLE GO -- Disable Clustered Index ALTER INDEX [PK_TableName] ON [dbo].[TableName] DISABLE GO -- Check that all the indexes are disabled SELECT OBJECT_NAME(OBJECT_ID), Name, type_desc, is_disabled FROM sys.indexes WHERE OBJECT_NAME(OBJECT_ID) = 'TableName' GO Next, let us build only the clustered index and see the output of all the indexes. -- Test 2: ALTER INDEX REBUILD -- Rebuliding should work fine ALTER INDEX [PK_TableName] ON [dbo].[TableName] REBUILD GO -- Check that only clustered index is enabled SELECT OBJECT_NAME(OBJECT_ID), Name, type_desc, is_disabled FROM sys.indexes WHERE OBJECT_NAME(OBJECT_ID) = 'TableName' GO Let us do final clean up. -- Clean up DROP TABLE [TableName] GO From the example, it is very clear that if you have built only clustered index when the nonclustered index is disabled, it still remains disabled. Do let me know if the idea is clear. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Index, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Difference Between DATETIME and DATETIME2

  - by pinaldave

  Yesterday I have written a very quick blog post on SQL SERVER – Difference Between GETDATE and SYSDATETIME and I got tremendous response for the same. I suggest you read that blog post before continuing this blog post today. I had asked people to honestly take part and share their view about above two system function. There are few emails as well few comments on the blog post asking question how did I come to know the difference between the same. The answer is real world issues. I was called in for performance tuning consultancy where I was asked very strange question by one developer. Here is the situation he was facing. System had a single table with two different column of datetime. One column was datelastmodified and second column was datefirstmodified. One of the column was DATETIME and another was DATETIME2. Developer was populating them with SYSDATETIME respectively. He was always thinking that the value inserted in the table will be the same. This table was only accessed by INSERT statement and there was no updates done over it in application.One fine day he ran distinct on both of this column and was in for surprise. He always thought that both of the table will have same data, but in fact they had very different data. He presented this scenario to me. I said this can not be possible but when looked at the resultset, I had to agree with him. Here is the simple script generated to demonstrate the problem he was facing. This is just a sample of original table. DECLARE @Intveral INT SET @Intveral = 10000 CREATE TABLE #TimeTable (FirstDate DATETIME, LastDate DATETIME2) WHILE (@Intveral > 0) BEGIN INSERT #TimeTable (FirstDate, LastDate) VALUES (SYSDATETIME(), SYSDATETIME()) SET @Intveral = @Intveral - 1 END GO SELECT COUNT(DISTINCT FirstDate) D_GETDATE, COUNT(DISTINCT LastDate) D_SYSGETDATE FROM #TimeTable GO SELECT DISTINCT a.FirstDate, b.LastDate FROM #TimeTable a INNER JOIN #TimeTable b ON a.FirstDate = b.LastDate GO SELECT * FROM #TimeTable GO DROP TABLE #TimeTable GO Let us see the resultset. You can clearly see from result that SYSDATETIME() does not populate the same value in the both of the field. In fact the value is either rounded down or rounded up in the field which is DATETIME. Event though we are populating the same value, the values are totally different in both the column resulting the SELF JOIN fail and display different DISTINCT values. The best policy is if you are using DATETIME use GETDATE() and if you are suing DATETIME2 use SYSDATETIME() to populate them with current date and time to accurately address the precision. As DATETIME2 is introduced in SQL Server 2008, above script will only work with SQL SErver 2008 and later versions. I hope I have answered few questions asked yesterday. Reference: Pinal Dave (http://www.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL DateTime, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Stored Procedure and Transactions

  - by pinaldave

  I just overheard the following statement – “I do not use Transactions in SQL as I use Stored Procedure“. I just realized that there are so many misconceptions about this subject. Transactions has nothing to do with Stored Procedures. Let me demonstrate that with a simple example. USE tempdb GO -- Create 3 Test Tables CREATE TABLE TABLE1 (ID INT); CREATE TABLE TABLE2 (ID INT); CREATE TABLE TABLE3 (ID INT); GO -- Create SP CREATE PROCEDURE TestSP AS INSERT INTO TABLE1 (ID) VALUES (1) INSERT INTO TABLE2 (ID) VALUES ('a') INSERT INTO TABLE3 (ID) VALUES (3) GO -- Execute SP -- SP will error out EXEC TestSP GO -- Check the Values in Table SELECT * FROM TABLE1; SELECT * FROM TABLE2; SELECT * FROM TABLE3; GO Now, the main point is: If Stored Procedure is transactional then, it should roll back complete transactions when it encounters any errors. Well, that does not happen in this case, which proves that Stored Procedure does not only provide just the transactional feature to a batch of T-SQL. Let’s see the result very quickly. It is very clear that there were entries in table1 which are not shown in the subsequent tables. If SP was transactional in terms of T-SQL Query Batches, there would be no entries in any of the tables. If you want to use Transactions with Stored Procedure, wrap the code around with BEGIN TRAN and COMMIT TRAN. The example is as following. CREATE PROCEDURE TestSPTran AS BEGIN TRAN INSERT INTO TABLE1 (ID) VALUES (11) INSERT INTO TABLE2 (ID) VALUES ('b') INSERT INTO TABLE3 (ID) VALUES (33) COMMIT GO -- Execute SP EXEC TestSPTran GO -- Check the Values in Tables SELECT * FROM TABLE1; SELECT * FROM TABLE2; SELECT * FROM TABLE3; GO -- Clean up DROP TABLE Table1 DROP TABLE Table2 DROP TABLE Table3 GO In this case, there will be no entries in any part of the table. What is your opinion about this blog post? Please leave your comments about it here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Stored Procedure, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – When are Statistics Updated – What triggers Statistics to Update

  - by pinaldave

  If you are an SQL Server Consultant/Trainer involved with Performance Tuning and Query Optimization, I am sure you have faced the following questions many times. When is statistics updated? What is the interval of Statistics update? What is the algorithm behind update statistics? These are the puzzling questions and more. I searched the Internet as well many official MS documents in order to find answers. All of them have provided almost similar algorithm. However, at many places, I have seen a bit of variation in algorithm as well. I have finally compiled the list of various algorithms and decided to share what was the most common “factor” in all of them. I would like to ask for your suggestions as whether following the details, when Statistics is updated, are accurate or not. I will update this blog post with accurate information after receiving your ideas. The answer I have found here is when statistics are expired and not when they are automatically updated. I need your help here to answer when they are updated. Permanent table If the table has no rows, statistics is updated when there is a single change in table. If the number of rows in a table is less than 500, statistics is updated for every 500 changes in table. If the number of rows in table is more than 500, statistics is updated for every 500+20% of rows changes in table. Temporary table If the table has no rows, statistics is updated when there is a single change in table. If the number of rows in table is less than 6, statistics is updated for every 6 changes in table. If the number of rows in table is less than 500, statistics is updated for every 500 changes in table. If the number of rows in table is more than 500, statistics is updated for every 500+20% of rows changes in table. Table variable There is no statistics for Table Variables. If you want to read further about statistics, I suggest that you read the white paper Statistics Used by the Query Optimizer in Microsoft SQL Server 2008. Let me know your opinions about statistics, as well as if there is any update in the above algorithm. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Question, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Statistics

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• MySQL – How to Find mysqld.exe with Command Prompt – Fix: ‘mysql’ is not recognized as an internal or external command, operable program or batch file

  - by Pinal Dave

  One of the most popular question I get after watching my MySQL courses on Pluralsight is that beginning users are not able to find where they have installed MySQL Server. The error they receive is as follows when they type mysqld command on their default command line. ‘mysql‘ is not recognized as an internal or external command, operable program or batch file. This error comes up if user try to execute mysqld command on default command prompt. The user should execute this command where mysql.exe file exists.  If you are using Windows Explorer you can easily search on your drive mysqld.exe and find the location of the file and execute the above command there. However, if you want to find out with command prompt the location of mysqld.exe file you can follow the direction here. Step 1: Open a command prompt Open command prompt from Start >> Run >> cmd >> enter Step 2: Change directory You need to change the default directory to root directory, hence type cd\ command on the prompt to change the default directory to c:\ . Here we are assuming that you have installed MySQL on your c: drive. If you have installed it on any other drive change the drive to that letter. Step 3: Search Drive Type the command dir mysqld.exe /s /p on the command prompt. It will search your directories and will list the directory where mysqld.exe is located. Step 4: Change Directory Now once again change your command prompt file location to the folder where your mysqld.exe is located. In my case it is located here in folder C:\Program Files\MySQL\MySQL Server 5.6\bin hence I will run following command: cd C:\Program Files\MySQL\MySQL Server 5.6\bin . Step 5: Execute mysqld.exe Now you can once again mysqld.exe on your command prompt. You can use this method to search pretty much any file with the help of command prompt. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: MySQL, PostADay, SQL, SQL Authority, SQL Query, SQL Tips and Tricks, T SQL

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• SQL SERVER – WRITELOG – Wait Type – Day 17 of 28

  - by pinaldave

  WRITELOG is one of the most interesting wait types. So far we have seen a lot of different wait types, but this log type is associated with log file which makes it interesting to deal with. From Book On-Line: WRITELOG Occurs while waiting for a log flush to complete. Common operations that cause log flushes are checkpoints and transaction commits. WRITELOG Explanation: This wait type is usually seen in the heavy transactional database. When data is modified, it is written both on the log cache and buffer cache. This wait type occurs when data in the log cache is flushing to the disk. During this time, the session has to wait due to WRITELOG. I have recently seen this wait type’s persistence at my client’s place, where one of the long-running transactions was stopped by the user causing it to roll back. In the future, I will see if I could re-create this situation once again on my machine to validate the relation. Reducing WRITELOG wait: There are several suggestions to reduce this wait stats: Move Transaction Log to Separate Disk from mdf and other files. Avoid cursor-like coding methodology and frequent committing of statements. Find the most active file based on IO stall time based on the script written over here. You can also use fn_virtualfilestats to find IO-related issues using the script mentioned over here. Check the IO-related counters (PhysicalDisk:Avg.Disk Queue Length, PhysicalDisk:Disk Read Bytes/sec and PhysicalDisk :Disk Write Bytes/sec) for additional details. Read about them over here. There are two excellent resources by Paul Randal, I suggest you understand the subject from those videos. The links to videos are here and here. 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 Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• SQL SERVER – Best Reference – Wait Type – Day 27 of 28

  - by pinaldave

  I have great learning experience to write my article series on Extended Event. This was truly learning experience where I have learned way more than I would have learned otherwise. Besides my blog series there was excellent quality reference available on internet which one can use to learn this subject further. Here is the list of resources (in no particular order): sys.dm_os_wait_stats (Book OnLine) – This is excellent beginning point and official documentations on the wait types description. SQL Server Best Practices Article by Tom Davidson – I think this document goes without saying the BEST reference available on this subject. Performance Tuning with Wait Statistics by Joe Sack – One of the best slide deck available on this subject. It covers many real world scenarios. Wait statistics, or please tell me where it hurts by Paul Randal – Notes from real world from SQL Server Skilled Master Paul Randal. The SQL Server Wait Type Repository… by Bob Ward – A thorough article on wait types and its resolution. A MUST read. Tracking Session and Statement Level Waits by by Jonathan Kehayias – A unique article on the subject where wait stats and extended events are together. Wait Stats Introductory References By Jimmy May – Excellent collection of the reference links. Great Resource On SQL Server Wait Types by Glenn Berry – A perfect DMV to find top wait stats. Performance Blog by Idera – In depth article on top of the wait statistics in community. I have listed all the reference I have found in no particular order. If I have missed any good reference, please leave a comment and I will add the reference in the list. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Tracking Session and Statement Level Waits 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 – FT_IFTS_SCHEDULER_IDLE_WAIT – Full Text – Wait Type – Day 13 of 28

  - by pinaldave

  In the last few days during this series, I got many question about this Wait type. It would be great if you read my original related wait stats query in the first post because I have filtered it out in WHERE clause. However, I still get questions about this being one of the most wait types they encounter. The truth is, this is a background task processing and it really does not matter and it should be filtered out. There are many new Wait types related to Full Text Search that are introduced in SQL Server 2008. If you run the following query, you will be able to find them in the list. Currently there is not enough information for all of them available on BOL or any other place. But don’t worry; I will write an in-depth article when I learn more about them. SELECT * FROM sys.dm_os_wait_stats WHERE wait_type LIKE 'FT_%' The result set will contain following rows. FT_RESTART_CRAWL FT_METADATA_MUTEX FT_IFTSHC_MUTEX FT_IFTSISM_MUTEX FT_IFTS_RWLOCK FT_COMPROWSET_RWLOCK FT_MASTER_MERGE FT_IFTS_SCHEDULER_IDLE_WAIT We have understood so far that there is not much information available. But the problem is when you have this Wait type, what should you do?  The answer is to filter them out for the moment (i.e, do not pay attention on them) and focus on other pressing issues in wait stats or performance tuning. Here are two of my informal suggestions, which are totally independent from wait stats: Turn off the Full Text Search service in your system if you are  not necessarily using it on your server. Learn proper Full Text Search methodology. You can get Michael Coles’ book: Pro Full-Text Search in SQL Server 2008. Now I invite you to speak out your suggestions or any input regarding Full Text-related best practices and wait stats issue. Please leave a comment. 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 – Introduction to Adaptive ETL Tool – How adaptive is your ETL?

  - by pinaldave

  I am often reminded by the fact that BI/data warehousing infrastructure is very brittle and not very adaptive to change. There are lots of basic use cases where data needs to be frequently loaded into SQL Server or another database. What I have found is that as long as the sources and targets stay the same, SSIS or any other ETL tool for that matter does a pretty good job handling these types of scenarios. But what happens when you are faced with more challenging scenarios, where the data formats and possibly the data types of the source data are changing from customer to customer?  Let’s examine a real life situation where a health management company receives claims data from their customers in various source formats. Even though this company supplied all their customers with the same claims forms, they ended up building one-off ETL applications to process the claims for each customer. Why, you ask? Well, it turned out that the claims data from various regional hospitals they needed to process had slightly different data formats, e.g. “integer” versus “string” data field definitions.  Moreover the data itself was represented with slight nuances, e.g. “0001124” or “1124” or “0000001124” to represent a particular account number, which forced them, as I eluded above, to build new ETL processes for each customer in order to overcome the inconsistencies in the various claims forms.  As a result, they experienced a lot of redundancy in these ETL processes and recognized quickly that their system would become more difficult to maintain over time. So imagine for a moment that you could use an ETL tool that helps you abstract the data formats so that your ETL transformation process becomes more reusable. Imagine that one claims form represents a data item as a string – acc_no(varchar) – while a second claims form represents the same data item as an integer – account_no(integer). This would break your traditional ETL process as the data mappings are hard-wired.  But in a world of abstracted definitions, all you need to do is create parallel data mappings to a common data representation used within your ETL application; that is, map both external data fields to a common attribute whose name and type remain unchanged within the application. acc_no(varchar) is mapped to account_number(integer) expressor Studio first claim form schema mapping account_no(integer) is also mapped to account_number(integer) expressor Studio second claim form schema mapping All the data processing logic that follows manipulates the data as an integer value named account_number. Well, these are the kind of problems that that the expressor data integration solution automates for you.  I’ve been following them since last year and encourage you to check them out by downloading their free expressor Studio ETL software. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Business Intelligence, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: ETL, SSIS

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• Developer’s Life – Every Developer is a Spiderman

  - by Pinal Dave

  I have to admit, Spiderman is my favorite superhero.  The most recent movie recently was released in theaters, so it has been at the front of my mind for some time. Spiderman was my favorite superhero even before the latest movie came out, but of course I took my whole family to see the movie as soon as I could!  Every one of us loved it, including my daughter.  We all left the movie thinking how great it would be to be Spiderman.  So, with that in mind, I started thinking about how we are like Spiderman in our everyday lives, especially developers. Let me list some of the reasons why I think every developer is a Spiderman. We have special powers, just like a superhero.  There is a reason that when there are problems or emergencies, we get called in, just like a superhero!  Our powers might not be the ability to swing through skyscrapers on a web, our powers are our debugging abilities, but there are still similarities! Spiderman never gives up.  He might not be the strongest superhero, and the ability to shoot web from your wrists is a pretty cool power, it’s not as impressive as being able to fly, or be invisible, or turn into a hulking green monster.  Developers are also human.  We have cool abilities, but our true strength lies in our willingness to work hard, find solutions, and go above and beyond to solve problems. Spiderman and developers have “spidey sense.”  This is sort of a joke in the comics and movies as well – that Spiderman can just tell when something is about to go wrong, or when a villain is just around the corner.  Developers also have a spidey sense about when a server is about to crash (usually at midnight on a Saturday). Spiderman makes a great superhero because he doesn’t look like one.  Clark Kent is probably fooling no one, hiding his superhero persona behind glasses.  But Peter Parker actually does blend in.  Great developers also blend in.  When they do their job right, no one knows they were there at all. “With great power comes great responsibility.”  There is a joke about developers (sometimes we even tell the jokes) about how if they are unhappy, the server or databases might mysteriously develop problems.  The truth is, very few developers would do something to harm a company’s computer system – they take their job very seriously.  It is a big responsibility. These are just a few of the reasons why I love Spiderman, why I love being a developer, and why I think developers are the greatest.  Let me know other reasons you love Spiderman and developers, or if you can shoot webs from your wrists – I might have a job for you. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Fix Error: Microsoft OLE DB Provider for SQL Server error ’80040e07' or Microsoft SQL Native Client error ’80040e07'

  - by pinaldave

  I quite often receive questions where users are looking for solution to following error: Microsoft OLE DB Provider for SQL Server error ’80040e07′ Syntax error converting datetime from character string. OR Microsoft SQL Native Client error ’80040e07′ Syntax error converting datetime from character string. If you have ever faced above error – I have a very simple solution for you. The solution is being very check date which is inserted in the datetime column. This error often comes up when application or user is attempting to enter an incorrect date into the datetime field. Here is one of the examples – one of the reader was using classing ASP Application with OLE DB provider for SQL Server. When he tried to insert following script he faced above mentioned error. INSERT INTO TestTable (ID, MyDate) VALUES (1, '01-Septeber-2013') The reason for the error was simple as he had misspelled September word. Upon correction of the word, he was able to successfully insert the value and error was not there. Incorrect values or the typo’s are not the only reason for this error. There can be issues with cast or convert as well. If you try to attempt following code using SQL Native Client or in your application you will also get similar errors. SELECT CONVERT (datetime, '01-Septeber-2013', 112) The reason here is very simple, any conversion attempt or any other kind of operation on incorrect date/time string can lead to the above error. If you not using embeded dynamic code in your application language but using attempting similar operation on incorrect datetime string you will get following error. Msg 241, Level 16, State 1, Line 2 Conversion failed when converting date and/or time from character string. Remember: Check your values of the string when you are attempting to convert them to string – either there can be incorrect values or they may be incorrectly formatted. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – 4 Tips for ETL Software IDE Developers

  - by pinaldave

  In a previous blog, I introduced the notion of Semantic Types. To an end-user, a seamlessly integrated semantic typing engine significantly increases the ease of use of an ETL IDE (integrated development environment, or developer studio). This led me to think about other ease-of-use issues I have encountered while building ETL applications. When I get stumped while programming, I find myself asking the variations on these questions: “How do I…?” “Now what?” “Why isn’t this working?” “Why do I have to redo the work I just did?” It seems to me that a good ETL IDE will anticipate these questions and seek to answer them before they are even asked. So here are my tips to help software vendors build developer IDEs that actually make development easier. How do I…? While developing an ETL application, have you ever asked yourself: “How do I set up the connection to my SQL Server database?”,“How do I import my table definitions from Access?”, etc. An easy answer might be “read the manual” but sometimes product manuals are not robust or easily accessible. So, integrating robust how-to instructions directly into your ETLstudio would help users get the information they need at the time they need it. Now what? IDEs in general know where you last clicked or performed an action using an input device such as a keyboard; so they should be able to reasonably predict the design context you are in and suggest the next steps accordingly. Context-sensitive suggestions based on the state of the user’s work will help users move forward in ETL application development. Why isn’t this working? Or why do I have to wait till I compile to be told about a critical design issue? If an ETL IDE is smart enough to signal to users what in their design structures is left to be completed or has been completed incorrectly, then the developer can spend much less time in the designàcompileàerror-correct loop. Just-in-time validation helps users detect and correct programming errors earlier in the ETL development life cycle. Why do I have to redo the work I just did? In ETL development, schemas, transformation rules, connectivity objects, etc., can be reused in various situations. Using mouse-clicks to build and manage libraries of reusable design objects implies that the application development effort should decrease over time and as the library acquires more objects. I met a great company at SQL Pass that is trying to address many of these usability issues. Check them out at www.expressor-software.com. What other ease-of-use suggestions do you have for ETL software vendors? Please post your valuable comments. ?Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: ETL

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• SQL SERVER – Importance of User Without Login – T-SQL Demo Script

  - by pinaldave

  Earlier I wrote a blog post about SQL SERVER – Importance of User Without Login and my friend and SQL Expert Vinod Kumar has written excellent follow up blog post about Contained Databases inside SQL Server 2012. Now lots of people asked me if I can also explain the same concept again so here is the small demonstration for it. Let me show you how login without user can help. Before we continue on this subject I strongly recommend that you read my earlier blog post here. In following demo I am going to demonstrate following situation. Login using the System Admin account Create a user without login Checking Access Impersonate the user without login Checking Access Revert Impersonation Give Permission to user without login Impersonate the user without login Checking Access Revert Impersonation Clean up USE [AdventureWorks2012] GO -- Step 1 : Login using the SA -- Step 2 : Create Login Less User CREATE USER [testguest] 9ITHOUT LOGIN WITH DEFAULT_SCHEMA=[dbo] GO -- Step 3 : Checking access to Tables SELECT * FROM sys.tables; -- Step 4 : Changing the execution contest EXECUTE AS USER   = 'testguest'; GO -- Step 5 : Checking access to Tables SELECT * FROM sys.tables; GO -- Step 6 : Reverting Permissions REVERT; -- Step 7 : Giving more Permissions to testguest user GRANT SELECT ON [dbo].[ErrorLog] TO [testguest]; GRANT SELECT ON [dbo].[DatabaseLog] TO [testguest]; GO -- Step 8 : Changing the execution contest EXECUTE AS USER   = 'testguest'; GO -- Step 9 : Checking access to Tables SELECT * FROM sys.tables; GO -- Step 10 : Reverting Permissions REVERT; GO -- Step 11: Clean up DROP USER [testguest]Step 3 GO Here is the step 9 we will be able to notice that how a user without login gets access to some of the data/object which we gave permission. What I am going to prove with this example? Well there can be different rights with different account. Once the login is authenticated it makes sense for impersonating a user with only necessary permissions to be used for further operation. Again this is very basic and fundamental example. There are lots of more points to be discussed as we go in future posts. Just do not take this blog post as a template and implement everything as it is. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Security, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – What the Business Says Is Not What the Business Wants

  - by pinaldave

  This blog post is written in response to T-SQL Tuesday hosted by Steve Jones. Steve raised a very interesting question; every DBA and Database Developer has already faced this situation. When I read the topic, I felt that I can write several different examples here. Today, I will cover this scenario, which seems quite amusing. Shrinking Database Earlier this year, I was working on SQL Server Performance Tuning consultancy; I had faced very interesting situation. No matter how much I attempt to reduce the fragmentation, I always end up with heavy fragmentation on the server. After careful research, I figured out that one of the jobs was continuously Shrinking the Database – which is a very bad practice. I have blogged about my experience over here SQL SERVER – SHRINKDATABASE For Every Database in the SQL Server. I removed the incorrect shrinking process right away; once it was removed, everything continued working as it should be. After a couple of days, I learned that one of their DBAs had put back the same DBCC process. I requested the Senior DBA to find out what is going on and he came up with the following reason: “Business Requirement.” I cannot believe this! Now, it was time for me to go deep into the subject. Moreover, it had become necessary to understand the need. After talking to the concerned people here, I understood what they needed. Please read the exact business need in their own language. The Shrinking “Business Need” “We shrink the database because if we take backup after shrinking the database, the size of the same is smaller. Once we take backup, we have to send it to our remote location site. Our business requirement is that we need to always make sure that the file is smallest when we transfer it to remote server.” The backup is not affected in any way if you shrink the database or not. The size of backup will be the same. After a couple of the tests, they agreed with me. Shrinking will create performance issues for the same as it will introduce heavy fragmentation in the database. The Real Solution The real business need was that they needed the smallest possible backup file. We finally implemented a quick solution which they are still using to date. The solution was compressed backup. I have written about this subject in detail few years before SQL SERVER – 2008 – Introduction to New Feature of Backup Compression. Compressed backup not only creates a small filesize but also increases the speed of the database as well. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Pinal Dave, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• SQL SERVER – CTE can be Updated

  - by Pinal Dave

  Today I have received a fantastic email from Matthew Spieth. SQL Server expert from Ohio. He recently had a great conversation with his colleagues in the office and wanted to make sure that everybody who reads this blog knows about this little feature which is commonly confused. Here is his statement and we will start our story with Matthew’s own statement: “Users often confuse CTE with Temp Table but technically they both are different, CTE are like Views and they can be updated just like views.“ Very true statement from Matthew. I totally agree with what he is saying. Just like him, I have enough, time came across a situation when developers think CTE is like temp table. When you update temp table, it remains in the scope of the temp table and it does not propagate it to the table based on which temp table is built. However, this is not the case when it is about CTE, when you update CTE, it updates underlying table just like view does. Here is the working example of the same built by Matthew to illustrate this behavior. Check the value in the base table first. USE AdventureWorks2012; -- Check - The value in the base table is updated SELECT Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738'; Now let us build CTE with the same data. ;WITH CTEUpd(ProductID, Name, ProductNumber, Color) AS( SELECT ProductID, Name, ProductNumber, Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738') Now let us update CTE with following code. -- Update CTE UPDATE CTEUpd SET Color = 'Rainbow'; Now let us check the BASE table based on which the CTE was built. -- Check - The value in the base table is updated SELECT Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738'; That’s it! You can update CTE and it will update the base table. Here is the script which you should execute all together. USE AdventureWorks2012; -- Check - The value in the base table is updated SELECT Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738'; -- Build CTE ;WITH CTEUpd(ProductID, Name, ProductNumber, Color) AS( SELECT ProductID, Name, ProductNumber, Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738') -- Update CTE UPDATE CTEUpd SET Color = 'Rainbow'; -- Check - The value in the base table is updated SELECT Color FROM [Production].[Product] WHERE ProductNumber = 'CA-6738'; If you are aware of such scenario, do let me know and I will post this on my blog with due credit to you. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL View, T SQL Tagged: CTE

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• SQL SERVER – Index Created on View not Used Often – Observation of the View – Part 2

  - by pinaldave

  Earlier, I have written an article about SQL SERVER – Index Created on View not Used Often – Observation of the View. I received an email from one of the readers, asking if there would no problems when we create the Index on the base table. Well, we need to discuss this situation in two different cases. Before proceeding to the discussion, I strongly suggest you read my earlier articles. To avoid the duplication, I am not going to repeat the code and explanation over here. In all the earlier cases, I have explained in detail how Index created on the View is not utilized. SQL SERVER – Index Created on View not Used Often – Limitation of the View 12 SQL SERVER – Index Created on View not Used Often – Observation of the View SQL SERVER – Indexed View always Use Index on Table As per earlier blog posts, so far we have done the following: Create a Table Create a View Create Index On View Write SELECT with ORDER BY on View However, the blog reader who emailed me suggests the extension of the said logic, which is as follows: Create a Table Create a View Create Index On View Write SELECT with ORDER BY on View Create Index on the Base Table Write SELECT with ORDER BY on View After doing the last two steps, the question is “Will the query on the View utilize the Index on the View, or will it still use the Index of the base table?“ Let us first run the Create example. USE tempdb GO IF EXISTS (SELECT * FROM sys.views WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[SampleView]')) DROP VIEW [dbo].[SampleView] GO IF EXISTS (SELECT * FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[mySampleTable]') AND TYPE IN (N'U')) DROP TABLE [dbo].[mySampleTable] GO -- Create SampleTable CREATE TABLE mySampleTable (ID1 INT, ID2 INT, SomeData VARCHAR(100)) INSERT INTO mySampleTable (ID1,ID2,SomeData) SELECT TOP 100000 ROW_NUMBER() OVER (ORDER BY o1.name), ROW_NUMBER() OVER (ORDER BY o2.name), o2.name FROM sys.all_objects o1 CROSS JOIN sys.all_objects o2 GO -- Create View CREATE VIEW SampleView WITH SCHEMABINDING AS SELECT ID1,ID2,SomeData FROM dbo.mySampleTable GO -- Create Index on View CREATE UNIQUE CLUSTERED INDEX [IX_ViewSample] ON [dbo].[SampleView] ( ID2 ASC ) GO -- Select from view SELECT ID1,ID2,SomeData FROM SampleView ORDER BY ID2 GO -- Create Index on Original Table -- On Column ID1 CREATE UNIQUE CLUSTERED INDEX [IX_OriginalTable] ON mySampleTable ( ID1 ASC ) GO -- On Column ID2 CREATE UNIQUE NONCLUSTERED INDEX [IX_OriginalTable_ID2] ON mySampleTable ( ID2 ) GO -- Select from view SELECT ID1,ID2,SomeData FROM SampleView ORDER BY ID2 GO Now let us see the execution plans for both of the SELECT statement. Before Index on Base Table (with Index on View): After Index on Base Table (with Index on View): Looking at both executions, it is very clear that with or without, the View is using Indexes. Alright, I have written 11 disadvantages of the Views. Now I have written one case where the View is using Indexes. Anybody who says that I am being harsh on Views can say now that I found one place where Index on View can be helpful. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL View, SQLServer, T SQL, Technology

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• SQL SERVER – Implementing IF … THEN in SQL SERVER with CASE Statements

  - by Pinal Dave

  Here is the question I received the other day in email. “I have business logic in my .net code and we use lots of IF … ELSE logic in our code. I want to move the logic to Stored Procedure. How do I convert the logic of the IF…ELSE to T-SQL. Please help.” I have previously received this answer few times. As data grows the performance problems grows more as well. Here is the how you can convert the logic of IF…ELSE in to CASE statement of SQL Server. Here are few of the examples: Example 1: If you are logic is as following: IF -1 < 1 THEN ‘TRUE’ ELSE ‘FALSE’ You can just use CASE statement as follows: -- SQL Server 2008 and earlier version solution SELECT CASE WHEN -1 < 1 THEN 'TRUE' ELSE 'FALSE' END AS Result GO -- SQL Server 2012 solution SELECT IIF ( -1 < 1, 'TRUE', 'FALSE' ) AS Result; GO If you are interested further about how IIF of SQL Server 2012 works read the blog post which I have written earlier this year . Well, in our example the condition which we have used is pretty simple but in the real world the logic can very complex. Let us see two different methods of how we an do CASE statement when we have logic based on the column of the table. Example 2: If you are logic is as following: IF BusinessEntityID < 10 THEN FirstName ELSE IF BusinessEntityID > 10 THEN PersonType FROM Person.Person p You can convert the same in the T-SQL as follows: SELECT CASE WHEN BusinessEntityID < 10 THEN FirstName WHEN BusinessEntityID > 10 THEN PersonType END AS Col, BusinessEntityID, Title, PersonType FROM Person.Person p However, if your logic is based on multiple column and conditions are complicated, you can follow the example 3. Example 3: If you are logic is as following: IF BusinessEntityID < 10 THEN FirstName ELSE IF BusinessEntityID > 10 AND Title IS NOT NULL THEN PersonType ELSE IF Title = 'Mr.' THEN 'Mister' ELSE 'No Idea' FROM Person.Person p You can convert the same in the T-SQL as follows: SELECT CASE WHEN BusinessEntityID < 10 THEN FirstName WHEN BusinessEntityID > 10 AND Title IS NOT NULL THEN PersonType WHEN Title = 'Mr.' THEN 'Mister' ELSE 'No Idea' END AS Col, BusinessEntityID, Title, PersonType FROM Person.Person p I hope this solution is good enough to convert the IF…ELSE logic to CASE Statement in SQL Server. Let me know if you need further information about the same. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Index Created on View not Used Often – Observation of the View

  - by pinaldave

  I always enjoy writing about concepts on Views. Views are frequently used concepts, and so it’s not surprising that I have seen so many misconceptions about this subject. To clear such misconceptions, I have previously written the article SQL SERVER – The Limitations of the Views – Eleven and more…. I also wrote a follow up article wherein I demonstrated that without even creating index on the basic table, the query on the View will not use the View. You can read about this demonstration over here: SQL SERVER – Index Created on View not Used Often – Limitation of the View 12. I promised in that post that I would also write an article where I would demonstrate the condition where the Index will be used. I got many responses suggesting that I can do that with using NOEXPAND; I agree. I have already written about this in my original summary article. Here is a way for you to see how Index created on View can be utilized. We will do the following steps on this exercise: Create a Table Create a View Create Index On View Write SELECT with ORDER BY on View USE tempdb GO IF EXISTS (SELECT * FROM sys.views WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[SampleView]')) DROP VIEW [dbo].[SampleView] GO IF EXISTS (SELECT * FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[mySampleTable]') AND TYPE IN (N'U')) DROP TABLE [dbo].[mySampleTable] GO -- Create SampleTable CREATE TABLE mySampleTable (ID1 INT, ID2 INT, SomeData VARCHAR(100)) INSERT INTO mySampleTable (ID1,ID2,SomeData) SELECT TOP 100000 ROW_NUMBER() OVER (ORDER BY o1.name), ROW_NUMBER() OVER (ORDER BY o2.name), o2.name FROM sys.all_objects o1 CROSS JOIN sys.all_objects o2 GO -- Create View CREATE VIEW SampleView WITH SCHEMABINDING AS SELECT ID1,ID2,SomeData FROM dbo.mySampleTable GO -- Create Index on View CREATE UNIQUE CLUSTERED INDEX [IX_ViewSample] ON [dbo].[SampleView] ( ID2 ASC ) GO -- Select from view SELECT ID1,ID2,SomeData FROM SampleView ORDER BY ID2 GO When we check the execution plan for this , we find it clearly that the Index created on the View is utilized. ORDER BY clause uses the Index created on the View. I hope this makes the puzzle simpler on how the Index is used on the View. Again, I strongly recommend reading my earlier series about the limitations of the Views found here: SQL SERVER – The Limitations of the Views – Eleven and more…. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL View, T SQL, Technology

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• SQL SERVER – Challenge – Puzzle – Usage of FAST Hint

  - by pinaldave

  I was recently working with various SQL Server Hints. After working for a day on various hints, I realize that for one hint, I am not able to come up with good example. The hint is FAST. Let us look at the definition of the FAST hint from the Book On-Line. FAST number_rows Specifies that the query is optimized for fast retrieval of the first number_rows. This is a nonnegative integer. After the first number_rows are returned, the query continues execution and produces its full result set. Now the question is in what condition this hint can be useful. I have tried so many different combination, I have found this hint does not make much performance difference, infect I did not notice any change in time taken to load the resultset. I noticed that this hint does not change number of the page read to return result. Now when there is difference in performance is expected because if you read the what FAST hint does is that it only returns first few results FAST – which does not mean there will be difference in performance. I also understand that this hint gives the guidance/suggestions/hint to query optimizer that there are only 100 rows are in expected resultset. This tricking the optimizer to think there are only 100 rows and which (may) lead to render different execution plan than the one which it would have taken in normal case (without hint). Again, not necessarily, this will happen always. Now if you read above discussion, you will find that basic understanding of the hint is very clear to me but I still feel that I am missing something. Here are my questions: 1) In what condition this hint can be useful? What is the case, when someone want to see first few rows early because my experience suggests that when first few rows are rendered remaining rows are rendered as well. 2) Is there any way application can retrieve the fast fetched rows from SQL Server? 3) Do you use this hint in your application? Why? When? and How? Here are few examples I have attempted during the my experiment and found there is no difference in execution plan except its estimated number of rows are different leading optimizer think that the cost is less but in reality that is not the case. USE AdventureWorks GO SET STATISTICS IO ON SET STATISTICS TIME ON GO --------------------------------------------- -- Table Scan with Fast Hint SELECT * FROM Sales.SalesOrderDetail GO SELECT * FROM Sales.SalesOrderDetail OPTION (FAST 100) GO --------------------------------------------- -- Table Scan with Where on Index Key SELECT * FROM Sales.SalesOrderDetail WHERE OrderQty = 14 GO SELECT * FROM Sales.SalesOrderDetail WHERE OrderQty = 14 OPTION (FAST 100) GO --------------------------------------------- -- Table Scan with Where on Index Key SELECT * FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID < 1000 GO SELECT * FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID < 1000 OPTION (FAST 100) GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Dedicated Access Control for SQL Server Express Edition – An error occurred while obtaining the dedicated administrator connection (DAC) port.

  - by pinaldave

  Recently I had faced very interesting situation. Due to some reason we were not able to login into the production server for one of client. The reason for the same was that server was very busy, we had to login into the system and bring server to normal situation. When all the attempts failed, I decided to login using Dedicated Administrator Connection (DAC). However when I attempted to connect using DAC it threw following error for me. C:\Users\pinald>sqlcmd -A -d master -S .\SQLEXPRESS Sqlcmd: Error: Microsoft SQL Server Native Client 11.0 : SQL Server Network Interfaces: An error occurred while obtaining the dedicated administrator connection (DAC) port. Make sure that SQL Browser is running, or check the error log for t he port number [xFFFFFFFF]. .Sqlcmd: Error: Microsoft SQL Server Native Client 11.0 : Login timeout expired.Sqlcmd: Error: Microsoft SQL Server Native Client 11.0 : A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections. For more information see SQL Server Books Online. I was bit taken a back as I knew that my commands are correct to login and if DAC does not work, there should be some serious reason for it. When inquired further about the SQL Server version I learned that it was SQL Server Express version deployed. To conserve resources, SQL Server Express does not listen on the DAC port. There is an additional step to be done if SQL Server Express has to be used with DAC. Enable TRACEFLAG on SQL Server Express will enable the connection by DAC possible. Here is the quick methods how one can enable DAC on SQL Server Express. Go to Start >> All Program >>Microsoft SQL Server (your version) >> Configuration Tools >> SQL Server Configuration Manager. Click on SQL Server Services >> Select your SQL Server Express version >> Right Click Properties >> select Startup Parameters Once on the Startup Parameter add the Startup parameter which is TRACEFLAG -T7806. Click on OK and RESTART SQL Server Express edition. Now once again try to connect to SQL Server Express edition and it will work just fine. This is absolutely documented method on BOL and SQL Server Express needs to be restarted. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Error Messages, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology Tagged: SQL Server Express

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• SQL SERVER – ColumnStore Index – Batch Mode vs Row Mode

  - by pinaldave

  What do you do when you are in a hurry and hear someone say things which you do not agree or is wrong? Well, let me tell you what I do or what I recently did. I was walking by and heard someone mentioning “Columnstore Index are really great as they are using Batch Mode which makes them seriously fast.” While I was passing by and I heard this statement my first reaction was I thought Columnstore Index can use both – Batch Mode and Row Mode. I stopped by even though I was in a hurry and asked the person if he meant that Columnstore indexes are seriously fast because they use Batch Mode all the time or Batch Mode is one of the reasons for Columnstore Index to be faster. He responded that Columnstore Indexes can run only in Batch Mode. However, I do not like to confront anybody without hearing their complete story. Honestly, I like to do information sharing and avoid confronting as much as possible. There are always ways to communicate the same positively. Well, this is what I did, I quickly pull up my earlier article on Columnstore Index and copied the script to SQL Server Management Studio. I created two versions of the script. 1) Very Large Table 2) Reasonably Small Table. I a query which uses columnstore index on both of the versions. I found very interesting result of the my tests. I saved my tests and sent it to the person who mentioned about that Columnstore Indexes are using Batch Mode only. He immediately acknowledged that indeed he was incorrect in saying that Columnstore Index uses only Batch Mode. What really caught my attention is that he also thanked me for sending him detail email instead of just having argument where he and I both were standing in the corridor and neither have no way to prove any theory. Here is the screenshots of the both the scenarios. 1) Columnstore Index using Batch Mode 2) Columnstore Index using Row Mode Here is the logic behind when Columnstore Index uses Batch Mode and when it uses Row Mode. A batch typically represents about 1000 rows of data. Batch mode processing also uses algorithms that are optimized for the multicore CPUs and increased memory throughput.  Batch mode processing spreads metadata access costs and overhead over all the rows in a batch.  Batch mode processing operates on compressed data when possible leading superior performance. Here is one last point – Columnstore Index can use Batch Mode or Row Mode but Batch Mode processing is only available in Columnstore Index. I hope this statement truly sums up the whole concept. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – guest User and MSDB Database – Enable guest User on MSDB Database

  - by pinaldave

  I have written a few articles recently on the subject of guest account. Here’s a quick list of these articles: SQL SERVER – Disable Guest Account – Serious Security Issue SQL SERVER – Force Removing User from Database – Fix: Error: Could not drop login ‘test’ as the user is currently logged in. SQL SERVER – Detecting guest User Permissions – guest User Access Status One of the advices which I gave in all the three blog posts was: Disable the guest user in the user-created database. Additionally, I have mentioned that one should let the user account become enabled in MSDB database. I got many questions asking if there is any specific reason why this should be kept enabled, questions like, “What is the reason that MSDB database needs guest user?” Honestly, I did not know that the concept of the guest user will create so much interest in the readers. So now let’s turn this blog post into questions and answers format. Q: What will happen if the guest user is disabled in MSDB database? A:  Lots of bad things will happen. Error 916 - Logins can connect to this instance of SQL Server but they do not have specific permissions in a database to receive the permissions of the guest user. Q: How can I determine if the guest user is enabled or disabled for any specific database? A: There are many ways to do this. Make sure that you run each of these methods with the context of the database. For an example for msdb database, you can run the following code: USE msdb; SELECT name, permission_name, state_desc FROM sys.database_principals dp INNER JOIN sys.server_permissions sp ON dp.principal_id = sp.grantee_principal_id WHERE name = 'guest' AND permission_name = 'CONNECT' There are many other methods to detect the guest user status. Read them here: Detecting guest User Permissions – guest User Access Status Q: What is the default status of the guest user account in database? A: Enabled in master, TempDb, and MSDB. Disabled in model database. Q: Why is the default status of the guest user disabled in model database? A: It is not recommended to enable the guest in user database as it can introduce serious security threat. It can seriously damage the database if configured incorrectly. Read more here: Disable Guest Account – Serious Security Issue Q: How to disable guest user? A: REVOKE CONNECT FROM guest Q: How to enable guest user? A: GRANT CONNECT TO guest Did I miss any critical question in the list? Please leave your question as a comment and I will add it to this list. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Security, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Validating Spatial Object as NULL using IsNULL

  - by pinaldave

  Follow up questions are the most fun part of writing a blog post. Earlier I wrote about SQL SERVER – Validating Spatial Object with IsValidDetailed Function and today I received a follow up question on the same subject. The question was mainly about how NULL is handled by spatial functions. Well, NULL is NULL. It is very easy to work with NULL. There are two different ways to validate if the passed in the value is NULL or not. 1) Using IsNULL Function IsNULL function validates if the object is null or not, if object is not null it will return you value 0 and if object is NULL it will return you the value NULL. DECLARE @p GEOMETRY = 'Polygon((2 2, 3 3, 4 4, 5 5, 6 6, 2 2))' SELECT @p.ISNULL ObjIsNull GO DECLARE @p GEOMETRY = NULL SELECT @p.ISNULL ObjIsNull GO 2) Using IsValidDetailed Function IsValidateDetails function validates if the object is valid or not. If the object is valid it will return 24400: Valid but if the object is not valid it will give message with the error number. In case object is NULL it will return the value as NULL. DECLARE @p GEOMETRY = 'Polygon((2 2, 3 3, 4 4, 5 5, 6 6, 2 2))' SELECT @p.IsValidDetailed() IsValid GO DECLARE @p GEOMETRY = NULL SELECT @p.IsValidDetailed() IsValid GO When to use what? Now you can see that there are two different ways to validate the NULL values. I personally have no preference about using one over another. However, there is one clear difference between them. In case of the IsValidDetailed Function the return value is nvarchar(max) and it is not always possible to compare the value with nvarchar(max). Whereas the ISNULL function returns the bit value of 0 when the object is null and it is easy to determine if the object is null or not in the case of ISNULL function. Additionally, ISNULL function does not check if the object is valid or not and will return the value 0 if the object is not NULL. Now you know even though either of the function can be used in place of each other both have very specific use case. Use the one which fits your business case. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Spatial Database, SQL Spatial

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