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  • SQL SERVER – Concurrancy Problems and their Relationship with Isolation Level

    - by pinaldave
    Concurrency is simply put capability of the machine to support two or more transactions working with the same data at the same time. This usually comes up with data is being modified, as during the retrieval of the data this is not the issue. Most of the concurrency problems can be avoided by SQL Locks. There are four types of concurrency problems visible in the normal programming. 1)      Lost Update – This problem occurs when there are two transactions involved and both are unaware of each other. The transaction which occurs later overwrites the transactions created by the earlier update. 2)      Dirty Reads – This problem occurs when a transactions selects data that isn’t committed by another transaction leading to read the data which may not exists when transactions are over. Example: Transaction 1 changes the row. Transaction 2 changes the row. Transaction 1 rolls back the changes. Transaction 2 has selected the row which does not exist. 3)      Nonrepeatable Reads – This problem occurs when two SELECT statements of the same data results in different values because another transactions has updated the data between the two SELECT statements. Example: Transaction 1 selects a row, which is later on updated by Transaction 2. When Transaction A later on selects the row it gets different value. 4)      Phantom Reads – This problem occurs when UPDATE/DELETE is happening on one set of data and INSERT/UPDATE is happening on the same set of data leading inconsistent data in earlier transaction when both the transactions are over. Example: Transaction 1 is deleting 10 rows which are marked as deleting rows, during the same time Transaction 2 inserts row marked as deleted. When Transaction 1 is done deleting rows, there will be still rows marked to be deleted. When two or more transactions are updating the data, concurrency is the biggest issue. I commonly see people toying around with isolation level or locking hints (e.g. NOLOCK) etc, which can very well compromise your data integrity leading to much larger issue in future. Here is the quick mapping of the isolation level with concurrency problems: Isolation Dirty Reads Lost Update Nonrepeatable Reads Phantom Reads Read Uncommitted Yes Yes Yes Yes Read Committed No Yes Yes Yes Repeatable Read No No No Yes Snapshot No No No No Serializable No No No No I hope this 400 word small article gives some quick understanding on concurrency issues and their relation to isolation level. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Introduction to Function SIGN

    - by pinaldave
    Yesterday I received an email from a friend asking how do SIGN function works. Well SIGN Function is very fundamental function. It will return the value 1, -1 or 0. If your value is negative it will return you negative -1 and if it is positive it will return you positive +1. Let us start with a simple small example. DECLARE @IntVal1 INT, @IntVal2 INT,@IntVal3 INT DECLARE @NumVal1 DECIMAL(4,2), @NumVal2 DECIMAL(4,2),@NumVal3 DECIMAL(4,2) SET @IntVal1 = 9; SET @IntVal2 = -9; SET @IntVal3 = 0; SET @NumVal1 = 9.0; SET @NumVal2 = -9.0; SET @NumVal3 = 0.0; SELECT SIGN(@IntVal1) IntVal1,SIGN(@IntVal2) IntVal2,SIGN(@IntVal3) IntVal3 SELECT SIGN(@NumVal1) NumVal1,SIGN(@NumVal2) NumVal2,SIGN(@NumVal2) NumVal3   The above function will give us following result set. You will notice that when there is positive value the function gives positive values and if the values are negative it will return you negative values. Also you will notice that if the data type is  INT the return value is INT and when the value passed to the function is Numeric the result also matches it. Not every datatype is compatible with this function.  Here is the quick look up of the return types. bigint -> bigint int/smallint/tinyint -> int money/smallmoney -> money numeric/decimal -> numeric/decimal everybody else -> float What will be the best example of the usage of this function that you will not have to use the CASE Statement. Here is example of CASE Statement usage and the same replaced with SIGN function. USE tempdb GO CREATE TABLE TestTable (Date1 SMALLDATETIME, Date2 SMALLDATETIME) INSERT INTO TestTable (Date1, Date2) SELECT '2012-06-22 16:15', '2012-06-20 16:15' UNION ALL SELECT '2012-06-24 16:15', '2012-06-22 16:15' UNION ALL SELECT '2012-06-22 16:15', '2012-06-22 16:15' GO -- Using Case Statement SELECT CASE WHEN DATEDIFF(d,Date1,Date2) > 0 THEN 1 WHEN DATEDIFF(d,Date1,Date2) < 0 THEN -1 ELSE 0 END AS Col FROM TestTable GO -- Using SIGN Function SELECT SIGN(DATEDIFF(d,Date1,Date2)) AS Col FROM TestTable GO DROP TABLE TestTable GO This was interesting blog post for me to write. Let me know your opinion. 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

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  • SQLAuthority News – My Evaluation of Singapore SharePoint Conference

    - by pinaldave
    Earlier this year I presented at SQLAuthority News – Presenting at South East Asia SharePoint Conference – Oct 26, 27, 2010 – Singapore. I felt very good to be presenting at Singapore as SharePoint Conference as I was the only SQL Speaker at the event. The event was filled with SharePoint enthusiasts and lots of other experts from all around the globe. The event was one of the best organized event, I attended in subcontinent. I just received my feedback score of the event. I was very much surprised and stunned. My ratting are very high as well, my demo were considered as one of the best demo of the whole event. I am not sure how much feedback I can share with community as organizer did not specify to me but I am very certain that I am allowed to share my own feedback. Speaker – 4.39 (best score 4.74, average 3.84) Contents – 4.37 (best score 4.39, average 3.65) Demo – 4.48 (best score, 4.48, average 3.61) I am very glad that all of my efforts to do presentations at SharePoint Conference are finally paid up. I was very much worried earlier if attendees will accept me or not as I am coming as speaker from foreign technology and no one knows me there. I must thank all of you for the same. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SharePoint, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, T SQL, Technology Tagged: SharePoint

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  • SQL SERVER – Tell me What You Want to Listen – My 2 TechED 2011 Sessions

    - by pinaldave
    I am going to present two sessions at TechEd India on March 25th, 2011. I would like to know what do you want me to cover in this session. Watch the video taken by my wife when I was preparing for the session. Sessions Date: March 25, 2011 Understanding SQL Server Behavioral Pattern – SQL Server Extended Events Date and Time: March 25, 2011 12:00 PM to 01:00 PM SQL Server Waits and Queues – Your Gateway to Perf. Troubleshooting Date and Time: March 25, 2011 04:15 PM to 05:15 PM I promise following for both of my sessions: I will share the scripts demonstrated in the session right at the end of the sessions The sessions will be 300-400 level but I promise to make the concept very simple Less slides and lots of meaningful Demos Session close to real life cases and scenarios Surprise gifts to best participants I promise to answer all the questions either in session or right after the hall after the session Lots of Technical Education and FUN! Please leave your comments with your expectation and if you are going to attend the session do let me know here. We will for sure meet at the event and do some interesting talk. You can read the abstract of the session over here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, T SQL, Technology Tagged: TechEd, TechEdIn

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  • SQLAuthority News – Stay Connected and Social Media

    - by pinaldave
    I think I have finally gotten back my faith in social media. If you are following my blog I am sure you are aware of my views on social media – SQLAuthority News – Social Media Confusion – Twitter, FaceBook, LinkedIn and Me. I was not happy about how social media was evolving. Whenever I go to Twitter, LinkedIn or Facebook, I noticed the same updates everywhere. I just thought I was wasting my time doing the same thing everywhere. I strongly believe that there is no dictator on internet. Nobody has authority over others, everybody can express their ideas as long as it is not violating others privacy and it is not morally wrong. I have decided that instead of trying to improve the world, I should change myself and adjust my needs. Here are few things I have done to relieve my social media confusion. Twitter I un-followed people who were taking up my time with too many updates. I un-followed people who hardly updated at all. I did not follow anybody else’s list, as I have no control over who other people follow. I follow not only serious SQL people but some fun stuff as well. I removed all my friends who were on Facebook and repeating the same updates on Twitter. I engage with them on Facebook. I followed people who are very conversational on Twitter. I let anybody follow me. I update all my blog posts through at least five tweets online. I decided to re-tweet at least five of my favorite tweets of the day, this way I force myself to remain active in the community. Follow me on Twitter! LinkedIn I updated my career and professional info on LinkedIn. I keep my LinkedIn profile updated with my latest jobs and career news. I let anybody connect with me on LinkedIn. I specify my email address in my profile, keeping it easy for those who want to add me. I read all the profile related updates of my connections – it is very valuable to know who is where and what changes are happening. I do not add my personal tweets or comments in LinkedIn profile. I just keep it professional. Link with me at LinkedIn Facebook I use Facebook only for personal friends. I visit all of my friends at regular intervals and make sure that they are really my friends. I often remove my friends from my Twitter list who are sending duplicate updates. I upload my family photos as well as family updates on Facebook, making sure that only my approved friends are able to read my updates. I keep my Facebook very personal and I often chat with my friends on Facebook chat. I am no longer confused about social media and I think I am using it appropriately. As I said, one cannot decide for others how to use social media, you can only decide for yourself. I have finally found my peace with social media. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Quiz and Video – Introduction to Discovering XML Data Type Methods

    - by pinaldave
    This blog post is inspired from SQL Interoperability Joes 2 Pros: A Guide to Integrating SQL Server with XML, C#, and PowerShell – SQL Exam Prep Series 70-433 – Volume 5. [Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to Discovering XML Data Type Methods – A Primer. In the article we discussed various basics terminology of the XML. The article further covers following important concepts of XML. What are XML Data Type Methods The query() Method The value() Method The exist() Method The modify() Method Above five are the most important concepts related to XML and SQL Server. There are many more things one has to learn but without beginners fundamentals one can’t learn the advanced  concepts. Let us have small quiz and check how many of you get the fundamentals right. Quiz 1.) Which method returns an XML fragment from the source XML? query( ) value( ) exist( ) modify( ) All of them Only query( ) and value( ) 2.) Which XML data type method returns a “1” if found and “0” if the specified XPath is not found in the source XML? query( ) value( ) exist( ) modify( ) All of them Only query( ) and value( ) 3.) Which XML data type method allows you to pick the data type of the value that is returned from the source XML? query( ) value( ) exist( ) modify( ) All of them Only query( ) and value( ) 4.) Which method will not work with a SQL SELECT statement? query( ) value( ) exist( ) modify( ) All of them Only query( ) and value( ) Now make sure that you write down all the answers on the piece of paper. Watch following video and read earlier article over here. If you want to change the answer you still have chance. Solution 1) 1 2) 3 3) 2 4) 4 Now compare let us check the answers and compare your answers to following answers. I am very confident you will get them correct. Available at USA: Amazon India: Flipkart | IndiaPlaza Volume: 1, 2, 3, 4, 5 Please leave your feedback in the comment area for the quiz and video. Did you know all the answers of the quiz? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Load Generator – Free Tool From CodePlex

    - by pinaldave
    One of the most common questions I receive is if there any tool available to generate load on SQL Server. Absolutely there is a fabulous free tool available to generate load on SQL Server on Codeplex. This tool was released in 2008 but it is still extremely relevant to generate the load on SQL Server as well works fabulously. CodePlex is a project initiated by Microsoft for hosting open source softwares. The best part of this SQL Server Load Generator is that users can run multiple simultaneous queries again SQL Server using different login account and different application name. The interface of the tool is extremely easy to use and very intuitive as well. One of the things which I felt needed improvement was a default configuration. As every single time when I was adding a query the default settings were showing up and I had to manually change that. However, when I went to Menu >> Tools >>Options I was really happy as it has options to change every single default which is available. Here one can give default username, password, database name as well various settings related to configuration. Additionally application logging is also possible through the options. A couple of other important points I noticed was the button to reset counters as well status bar containing useful information of Total Threads, Completed Queries and Failed Queries. I use this frequently for my load testing. What tool do you use for SQL Server Load Generator? Download SQL Load Generator 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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  • SQLAuthority News – NuoDB MeetUp on Nov 8, 2012 in Seattle

    - by pinaldave
    I am pleased to let you know that I will be attending again this year’s SQLPASS conference in Seattle and look forward to meeting all of you while at the conference. In the next two weeks, I will provide you with a full agenda of where I will be during PASS. During the week, I will also be stopping by at the NuoDB MeetUp, which will be held close by at the Edge Grill at 1522 6th Ave in Seattle on Thursday, November 8th. This will be an excellent opportunity for you to learn more about their brand new distributed, peer-to-peer database solution, which I believe will revolutionize SQL cloud database technology in the 21th century.  I have been personally following NuoDB for months now and am very excited about the architecture and capabilities of this innovative product. Wiqar Chaudry, NuoDB technology evangelist, will give a presentation and demonstration of their elastically scalable SQL cloud database in this Meetup event.  Prior to joining NuoDB, Wiqar was a Senior Architect at Epsilon, the data intelligence company with big brand name customers in insurance, consumer goods, etc.  He’s also going to discuss how NuoDB compares with Azure, the hometown favorite, and why cloud-based SQL deployment will pave the way for the future. I will be at the NuoDB MeetUp to briefly talk about my own experiences with NuoDB and will be giving away some signed copies of my latest book as well will have some interesting goodies. So please join me and the NuoDB team at their Meetup event. RSVP here. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: NuoDB

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  • SQL SERVER – Weekly Series – Memory Lane – #007

    - by pinaldave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 Find Stored Procedure Related to Table in Database – Search in All Stored Procedure In 2006 I wrote a small script which will help user  find all the Stored Procedures (SP) which are related to one or more specific tables. This was quite a popular script however, in SQL Server 2012 the same can be achieved using new DMV sys.sql-expression_dependencies. I recently blogged about it over Find Referenced or Referencing Object in SQL Server using sys.sql_expression_dependencies. 2007 SQL SERVER – Versions, CodeNames, Year of Release 1993 – SQL Server 4.21 for Windows NT 1995 – SQL Server 6.0, codenamed SQL95 1996 – SQL Server 6.5, codenamed Hydra 1999 – SQL Server 7.0, codenamed Sphinx 1999 – SQL Server 7.0 OLAP, codenamed Plato 2000 – SQL Server 2000 32-bit, codenamed Shiloh (version 8.0) 2003 – SQL Server 2000 64-bit, codenamed Liberty 2005 – SQL Server 2005, codenamed Yukon (version 9.0) 2008 – SQL Server 2008, codenamed Katmai (version 10.0) 2011 – SQL Server 2008, codenamed Denali (version 11.0) Search String in Stored Procedure Searching sting in the stored procedure is one of the most frequent task developer do. They might be searching for a table, view or any other details. I have written a script to do the same in SQL Server 2000 and SQL Server 2005. This is worth bookmarking blog post. There is an alternative way to do the same as well here is the example. 2008 SQL SERVER – Refresh Database Using T-SQL NO! Some of the questions have a single answer NO! You may want to read the question in the original blog post. I had a great time saying No! SQL SERVER – Delete Backup History – Cleanup Backup History SQL Server stores history of all the taken backup forever. History of all the backup is stored in the msdb database. Many times older history is no more required. Following Stored Procedure can be executed with a parameter which takes days of history to keep. In the following example 30 is passed to keep a history of month. 2009 Stored Procedure are Compiled on First Run – SP taking Longer to Run First Time Is stored procedure pre-compiled? Why the Stored Procedure takes a long time to run for the first time?  This is a very common questions often discussed by developers and DBAs. There is an absolutely definite answer but the question has been discussed forever. There is a misconception that stored procedures are pre-compiled. They are not pre-compiled, but compiled only during the first run. For every subsequent runs, it is for sure pre-compiled. Read the entire article for example and demonstration. Removing Key Lookup – Seek Predicate – Predicate – An Interesting Observation Related to Datatypes This is one of the most important performance tuning lesson on my blog. I suggest this weekend you spend time reading them and let me know what you think about the concepts which I have demonstrated in the four part series. Part 1 | Part 2 | Part 3 | Part 4 Seek Predicate is the operation that describes the b-tree portion of the Seek. Predicate is the operation that describes the additional filter using non-key columns. Based on the description, it is very clear that Seek Predicate is better than Predicate as it searches indexes whereas in Predicate, the search is on non-key columns – which implies that the search is on the data in page files itself. Policy Based Management – Create, Evaluate and Fix Policies This article will cover the most spectacular feature of SQL Server – Policy-based management and how the configuration of SQL Server with policy-based management architecture can make a powerful difference. Policy based management is loaded with several advantages. It can help you implement various policies for reliable configuration of the system. It also provides additional administration assistance to DBAs and helps them effortlessly manage various tasks of SQL Server across the enterprise. 2010 Recycle Error Log – Create New Log file without Server Restart Once I observed a DBA to restaring the SQL Server when he needed new error log file. This was funny and sad both at the same time. There is no need to restart the server to create a new log file or recycle the log file. You can run sp_cycle_errorlog and achieve the same result. Get Database Backup History for a Single Database Simple but effective script! Reducing CXPACKET Wait Stats for High Transactional Database The subject is very complex and I have done my best to simplify the concept. In simpler words, when a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. Threads which came first have to wait for the slower thread to finish. The Wait by a specific completed thread is called CXPACKET Wait Stat. Information Related to DATETIME and DATETIME2 There are quite a lot of confusion with DATETIME and DATETIME2. DATETIME2 is also one of the underutilized datatype of SQL Server.  In this blog post I have written a follow up of the my earlier datetime series where I clarify a few of the concepts related to datetime. Difference Between GETDATE and SYSDATETIME Difference Between DATETIME and DATETIME2 – WITH GETDATE Difference Between DATETIME and DATETIME2 2011 Introduction to CUME_DIST – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function CUME_DIST(). This function provides cumulative distribution value. It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. Introduction to FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical functions FIRST_VALUE() and LAST_VALUE(). This function returns first and last value from the list. It will be very difficult to explain this in words so I’d like to attempt to explain its function through a brief example. Instead of creating a new table, I will be using the AdventureWorks sample database as most developers use that for experiment purposes. OVER clause with FIRST _VALUE and LAST_VALUE – Analytic Functions Introduced in SQL Server 2012 – ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING “Don’t you think there is bug in your first example where FIRST_VALUE is remain same but the LAST_VALUE is changing every line. I think the LAST_VALUE should be the highest value in the windows or set of result.” Puzzle – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY You can see that row number 2, 3, 4, and 5 has same SalesOrderID = 43667. The FIRST_VALUE is 78 and LAST_VALUE is 77. Now if these function was working on maximum and minimum value they should have given answer as 77 and 80 respectively instead of 78 and 77. Also the value of FIRST_VALUE is greater than LAST_VALUE 77. Why? Explain in detail. Introduction to LEAD and LAG – Analytic Functions Introduced in SQL Server 2012 SQL Server 2012 introduces new analytical function LEAD() and LAG(). This functions accesses data from a subsequent row (for lead) and previous row (for lag) in the same result set without the use of a self-join . It will be very difficult to explain this in words so I will attempt small example to explain you this function. Instead of creating new table, I will be using AdventureWorks sample database as most of the developer uses that for experiment. A Real Story of Book Getting ‘Out of Stock’ to A 25% Discount Story Available Our book was out of stock in 48 hours of it was arrived in stock! We got call from the online store with a request for more copies within 12 hours. But we had printed only as many as we had sent them. There were no extra copies. We finally talked to the printer to get more copies. However, due to festivals and holidays the copies could not be shipped to the online retailer for two days. We knew for sure that they were going to be out of the book for 48 hours. This is the story of how we overcame that situation! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Reseting Identity Values for All Tables

    - by pinaldave
    Sometime email requesting help generates more questions than the motivation to answer them. Let us go over one of the such examples. I have converted the complete email conversation to chat format for easy consumption. I almost got a headache after around 20 email exchange. I am sure if you can read it and feel my pain. DBA: “I deleted all of the data from my database and now it contains table structure only. However, when I tried to insert new data in my tables I noticed that my identity values starts from the same number where they actually were before I deleted the data.” Pinal: “How did you delete the data?” DBA: “Running Delete in Loop?” Pinal: “What was the need of such need?” DBA: “It was my development server and I needed to repopulate the database.” Pinal: “Oh so why did not you use TRUNCATE which would have reset the identity of your table to the original value when the data got deleted? This will work only if you want your database to reset to the original value. If you want to set any other value this may not work.” DBA: (silence for 2 days) DBA: “I did not realize it. Meanwhile I regenerated every table’s schema and dropped the table and re-created it.” Pinal: “Oh no, that would be extremely long and incorrect way. Very bad solution.” DBA: “I understand, should I just take backup of the database before I insert the data and when I need, I can use the original backup to restore the database. This way I will have identity beginning with 1.” Pinal: “This going totally downhill. It is wrong to do so on multiple levels. Did you even read my earlier email about TRUNCATE.” DBA: “Yeah. I found it in spam folder.” Pinal: (I decided to stay silent) DBA: (After 2 days) “Can you provide me script to reseed identity for all of my tables to value 1 without asking further question.” Pinal: USE DATABASE; EXEC sp_MSForEachTable ' IF OBJECTPROPERTY(object_id(''?''), ''TableHasIdentity'') = 1 DBCC CHECKIDENT (''?'', RESEED, 1)' GO Our conversation ended here. If you have directly jumped to this statement, I encourage you to read the conversation one time. There is difference between reseeding identity value to 1 and reseeding it to original value – I will write an another blog post on this subject in future. 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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  • SQLAuthority News – Featuring in Call Me Maybe The Developer Way – Pluralsight Video

    - by pinaldave
    Is SQL boring? Not at all. SQL is fun – one has to know how to maximize the fun while working with SQL Server. Earlier I was invited to participate in the video Pluralsight. I am sure all of you know that I have authored 3 SQL Server Learning courses with Pluralsight – 1) SQL Server Q and A 2) SQL Server Performance Tuning and 3) SQL Server Indexing. Before I say anything I suggest all of you watch the following video. Make sure that you pay special attention after 0 minute and 36 seconds. What I can say about this. I am just fortunate to be part of the history in the making. There are more than 53 super cool celebrities in this video. In this just over 3 minute video there are so many story lines. I must congratulate director Megan and creative assistant Mari for excellent work. There are so many fun moments in this small video. Let me list my top five moments. @John_Papa ‘s dance at second 14 @julielerman playing with cute doggy The RACE between @josepheames and @bruthafish – the end is hilarious The black belt moment by @boedie @stwool relaxing on something strange! Well, this is indeed a great short film. This video demonstrates how cool is the culture of Pluralsight and how fun loving they are. A good organization provides an environment to its employees and partners to have maximum fun while they all become part of the success story. Hats off to Aaron Skonnard for producing this fun loving video. Well, after listening to this song for multiple times, I decided to give a call to Pluralsight. If you want, you can call them at +1 (801) 784-9032 or send an email to james-cole at pluralsight.com . What are your top five favorite moments? List it in comments and you may win Pluralsight subscription. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: About Me, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – A Puzzle Part 4 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value

    - by pinaldave
    It seems like every weekend I get a new puzzle in my mind. Before continuing I suggest you read my previous posts here where I have shared earlier puzzles. A Puzzle – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value  A Puzzle Part 2 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value A Puzzle Part 3 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value After reading above three posts, I am very confident that you all will be ready for the next set of puzzles now. First execute the script which I have written here. Now guess what will be the next value as requested in the query. USE TempDB GO -- Create sequence CREATE SEQUENCE dbo.SequenceID AS DECIMAL(3,0) START WITH 1 INCREMENT BY -1 MINVALUE 1 MAXVALUE 3 CYCLE NO CACHE; GO SELECT next value FOR dbo.SequenceID; -- Guess the number SELECT next value FOR dbo.SequenceID; -- Clean up DROP SEQUENCE dbo.SequenceID; GO Please note that Starting value is 1, Increment value is the negative value of -1 and Minimum value is 3. Now let us first assume how this will work out. In our example of the sequence starting value is equal to 1 and decrement value is -1, this means the value should decrement from 1 to 0. However, the minimum value is 1. This means the value cannot further decrement at all. What will happen here? The natural assumption is that it should throw an error. How many of you are assuming about query will throw an ERROR? Well, you are WRONG! Do not blame yourself, it is my fault as I have told you only half of the story. Now if you have voted for error, let us continue running above code in SQL Server Management Studio. The above script will give the following output: Isn’t it interesting that instead of error out it is giving us result value 3. To understand the answer about the same, carefully observe the original syntax of creating SEQUENCE – there is a keyword CYCLE. This keyword cycles the values between the minimum and maximum value and when one of the range is exhausted it cycles the values from the other end of the cycle. As we have negative incremental value when query reaches to the minimum value or lower end it will cycle it from the maximum value. Here the maximum value is 3 so the next logical value is 3. If your business requirement is such that if sequence reaches the maximum or minimum value, it should throw an error, you should not use the keyword cycle, and it will behave as discussed. I hope, you are enjoying the puzzles as much as I am enjoying it. If you have any interesting puzzle to share, please do share with me and I will share this on blog with due credit to you. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • SQL SERVER 2008 – 2011 – Declare and Assign Variable in Single Statement

    - by pinaldave
    Many of us are tend to overlook simple things even if we are capable of doing complex work. In SQL Server 2008, inline variable assignment is available. This feature exists from last 3 years, but I hardly see its utilization. One of the common arguments was that as the project migrated from the earlier version, the feature disappears. I totally accept this argument and acknowledge it. However, my point is that this new feature should be used in all the new coding – what is your opinion? The code which we used in SQL Server 2005 and the earlier version is as follows: DECLARE @iVariable INT, @vVariable VARCHAR(100), @dDateTime DATETIME SET @iVariable = 1 SET @vVariable = 'myvar' SET @dDateTime = GETDATE() SELECT @iVariable iVar, @vVariable vVar, @dDateTime dDT GO The same should be re-written as following: DECLARE @iVariable INT = 1, @vVariable VARCHAR(100) = 'myvar', @dDateTime DATETIME = GETDATE() SELECT @iVariable iVar, @vVariable vVar, @dDateTime dDT GO I have started to use this new method to assign variables as I personally find it very easy to read as well write. Do you still use the earlier method to declare and assign variables? If yes, is there any particular reason or just an old routine? I am interested to hear about this. 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, T SQL, Technology

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  • SQL SERVER – Using MAXDOP 1 for Single Processor Query – SQL in Sixty Seconds #008 – Video

    - by pinaldave
    Today’s SQL in Sixty Seconds video is inspired from my presentation at TechEd India 2012 on Speed up! – Parallel Processes and Unparalleled Performance. There are always special cases when it is about SQL Server. There are always few queries which gives optimal performance when they are executed on single processor and there are always queries which gives optimal performance when they are executed on multiple processors. I will be presenting the how to identify such queries as well what are the best practices related to the same. In this quick video I am going to demonstrate if the query is giving optimal performance when running on single CPU how one can restrict queries to single CPU by using hint OPTION (MAXDOP 1). More on Errors: Difference Temp Table and Table Variable – Effect of Transaction Effect of TRANSACTION on Local Variable – After ROLLBACK and After COMMIT Debate – Table Variables vs Temporary Tables – Quiz – Puzzle – 13 of 31 I encourage you to submit your ideas for SQL in Sixty Seconds. We will try to accommodate as many as we can. 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 Tips and Tricks, SQLServer, T SQL, Video

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  • SQL SERVER – ERROR – FIX – Msg 3702, Level 16, State 3, Line 1 Cannot drop database “MyDBName” because it is currently in use

    - by pinaldave
    I often go to do various seminars and presentations at various organizations. During presentations I often create and drop various databases for demonstrations purpose. Recently in one of the presentations, I tried to remove my recently created database, I got following error. Msg 3702, Level 16, State 3, Line 1 Cannot drop database “MyDBName” because it is currently in use. The reason was very simple as my database was in use by another session or window. I had option that I should go and find open session and close it right away; later followed by dropping the database. As I was in rush I quickly wrote down following code and I was able to successfully drop the database. USE MASTER GO ALTER DATABASE MyDBName SET SINGLE_USER WITH ROLLBACK IMMEDIATE; DROP DATABASE MyDBName GO Please note that I am doing all this on my demonstrations, do not run above code on production without proper approvals and supervisions. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Identifying Column Data Type of uniqueidentifier without Querying System Tables

    - by pinaldave
    I love interesting conversations with related to SQL Server. One of my friends Madhivanan always comes up with an interesting point of conversation. Here is one of the conversation between us. I am very confident this blog post will for sure enable you with some new knowledge. Madhi: How do I know if any table has a uniqueidentifier column used in it? Pinal:  I am sure you know that you can do it through some DMV or catalogue views. Madhi: I know that but how can we do that without using DMV or catalogue views? Pinal: Hm… what can I use? Madhi: You can use table name. Pinal: Easy, just say SELECT YourUniqueIdentCol FROM Table. Madhi: Hold on, the question seems to be not clear to you – you do know the name of the column. The matter of the fact, you do not know if the table has uniqueidentifier column. Only information you have is table name. Pinal: Madhi, this seems like you are changing the question when I am close to answer. Madhi: Well, are you clear now? Let me say it again – How do I know if any table has a uniqueidentifier column and what is its value without using any DMV or System Catalogues? Only information you know is table name and you are allowed to return any kind of error if table does not have uniqueidentifier column. Pinal: Do you know the answer? Madhi: Yes. I just wanted to test your knowledge about SQL. Pinal: I will have to think. Let me accept I do not know it right away. Can you share the answer please? Madhi: I won! Here it goes! Pinal: When I have friends like you – who needs enemies? Madhi: (laughter which did not stop for a minute). CREATE TABLE t ( GuidCol UNIQUEIDENTIFIER DEFAULT newsequentialid() ROWGUIDCOL, data VARCHAR(60) ) INSERT INTO t (data) SELECT 'test' INSERT INTO t (data) SELECT 'test1' SELECT $rowguid FROM t DROP TABLE t This is indeed very interesting to me. Please note that this is not the optimal way and there will be many other ways to retrieve uniqueidentifier name and value. What I learned from this was if I am in a rush to check if the table has uniqueidentifier and I do not know the name of the same, I can use SELECT TOP (1) $rowguid and quickly know the name of the column. I can later use the same columnname in my query. Madhi did teach me this new trick. Did you know this? What are other ways to get the check uniqueidentifier column existence in a database? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Validating Unique Columnname Across Whole Database

    - by pinaldave
    I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. Asker: “Our business requirement is when we add new column we want it unique across current database.” Pinal: “Why do you have such requirement?” Asker: “Do you know the solution?” Pinal: “Sure I can come up with the answer but it will help me to come up with an optimal answer if I know the business need.” Asker: “Thanks – what will be the answer in that case.” Pinal: “Honestly I am just curious about the reason why you need your column name to be unique across database.” (Silence) Pinal: “Alright – here is the answer – I guess you do not want to tell me reason.” Option 1: Check if Column Exists in Current Database IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn') BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END Option 2: Check if Column Exists in Current Database in Specific Table IF EXISTS (  SELECT * FROM sys.columns WHERE Name = N'NameofColumn' AND OBJECT_ID = OBJECT_ID(N'tableName')) BEGIN SELECT 'Column Exists' -- add other logic END ELSE BEGIN SELECT 'Column Does NOT Exists' -- add other logic END I guess user did not want to share the reason why he had a unique requirement of having column name unique across databases. Here is my question back to you – have you faced a similar situation ever where you needed unique column name across a database. If not, can you guess what could be the reason for this kind of requirement?  Additional Reference: SQL SERVER – Query to Find Column From All Tables of Database Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL System Table, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Fix: Error: 8117: Operand data type bit is invalid for sum operator

    - by pinaldave
    Here is the very interesting error I received from a reader. He has very interesting question. He attempted to use BIT filed in the SUM aggregation function and he got following error. He went ahead with various different datatype (i.e. INT, TINYINT etc) and he was able to do the SUM but with BIT he faced the problem. Error Received: Msg 8117, Level 16, State 1, Line 1 Operand data type bit is invalid for sum operator. Reproduction of the error: Set up the environment USE tempdb GO -- Preparing Sample Data CREATE TABLE TestTable (ID INT, Flag BIT) GO INSERT INTO TestTable (ID, Flag) SELECT 1, 0 UNION ALL SELECT 2, 1 UNION ALL SELECT 3, 0 UNION ALL SELECT 4, 1 GO SELECT * FROM TestTable GO Following script will work fine: -- This will work fine SELECT SUM(ID) FROM TestTable GO However following generate error: -- This will generate error SELECT SUM(Flag) FROM TestTable GO The workaround is to convert or cast the BIT to INT: -- Workaround of error SELECT SUM(CONVERT(INT, Flag)) FROM TestTable GO Clean up the setup -- Clean up DROP TABLE TestTable GO Workaround: As mentioned in above script the workaround is to covert the bit datatype to another friendly data types like INT, TINYINT etc. 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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  • SQLAuthority News – 6th Anniversary and 50 Million Views and Over 2300 Blog Posts – Thank You Thank You

    - by pinaldave
    Six years ago, I started this SQLAuthority.com blog. There are so many things I want to say today – it is very very emotional. Instead of writing long I am including few images and cartoons. Last month we have also reached 50 Million Total Views on this blog. Here is the screen captured at that time. Click Image to Enlarge In 6 years there are total 2192 days (including 2 leap year day) and my total blog post count is 2300. That means I have been blogging more than 1 blog post every day. Here is the quick glance to all the numbers. Here you can find the list of all the 2300 blog posts. I am very glad to see my many of the friends stay in USA, India, United Kingdom, Canada and Australia in that order. You can see the geographic distribution of the support I receive on the blog from worldwide. On this day I would like to call out one 2 individuals who contribute equally or more in my success. When I started this blog 6 years ago, I was walking alone. After 2 years my wife Nupur joined my journey and 3 years later my daughter Shaivi joined the journey. Here is the example of the common conversation among us almost every day - Shaivi: Daddy, play catch-catch. Nupur: Shaivi, daddy will play with you once he finishes tomorrow’s blog. Shaivi: Daddy, Finish Blog. Okey. I play catch-catch (alone). SQLAuthority Family Well, thank you very much! We all love you! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: About Me, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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  • SQLAuthority News – Download Whitepaper – Choosing a Tabular or Multidimensional Modeling Experience in SQL Server 2012 Analysis Services

    - by pinaldave
    Data modeling is the most important task for any BI professional. Matter of the fact, the biggest challenge is to organizing disparate data into an analytic model that effectively and efficiently supports the reporting and analysis. SQL Server 2012 introduces BI Semantic Model (BISM), a single model that can support a broad range of reporting and analysis while blending two Analysis Services modeling experiences behind the scenes. Multidimensional modeling – enables BI professionals to create sophisticated multidimensional cubes using traditional online analytical processing (OLAP). Tabular modeling – provides self-service data modeling capabilities to business and data analysts. As data modeling is evolving and business needs are growing new technologies and tools are emerging to help end users to make the necessary adjustment to the reporting and analysis needs. This white paper is will provide practical guidance to help you decide which SQL Server 2012 Analysis Services modeling experience – tabular or multidimensional. Do let me know what do is your opinion as a comment. In simple word – I would like to know when will you use Tabular modeling and when Multidimensional modeling? Download Choosing a Tabular or Multidimensional Modeling Experience in SQL Server 2012 Analysis Services Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Business Intelligence, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, T SQL, Technology

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  • SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2

    - by pinaldave
    Social media has created an Always Connected World for us. Recently I enrolled myself to learn new technologies as a student. I had decided to focus on learning and decided not to stay connected on the internet while I am in the learning session. On the second day of the event after the learning was over, I noticed lots of notification from my friend on my various social media handle. He had connected with me on Twitter, Facebook, Google+, LinkedIn, YouTube as well SMS, WhatsApp on the phone, Skype messages and not to forget with a few emails. I right away called him up. The problem was very unique – let us hear the problem in his own words. “Pinal – we are in big trouble we are not able to figure out what is going on. Our product details table is continuously loosing rows. Lots of rows have disappeared since morning and we are unable to find why the rows are getting deleted. We have made sure that there is no DELETE command executed on the table as well. The matter of the fact, we have removed every single place the code which is referencing the table. We have done so many crazy things out of desperation but no luck. The rows are continuously deleted in a random pattern. Do you think we have problems with intrusion or virus?” After describing the problems he had pasted few rants about why I was not available during the day. I think it will be not smart to post those exact words here (due to many reasons). Well, my immediate reaction was to get online with him. His problem was unique to him and his team was all out to fix the issue since morning. As he said he has done quite a lot out in desperation. I started asking questions from audit, policy management and profiling the data. Very soon I realize that I think this problem was not as advanced as it looked. There was no intrusion, SQL Injection or virus issue. Well, long story short first - It was a very simple issue of foreign key created with ON UPDATE CASCADE and ON DELETE CASCADE.  CASCADE allows deletions or updates of key values to cascade through the tables defined to have foreign key relationships that can be traced back to the table on which the modification is performed. ON DELETE CASCADE specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted. ON UPDATE CASCADE specifies that if an attempt is made to update a key value in a row, where the key value is referenced by foreign keys in existing rows in other tables, all of the foreign key values are also updated to the new value specified for the key. (Reference: BOL) In simple words – due to ON DELETE CASCASE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. In my friend’s case, they had two tables, Products and ProductDetails. They had created foreign key referential integrity of the product id between the table. Now the as fall was up they were updating their catalogue. When they were updating the catalogue they were deleting products which are no more available. As the changes were cascading the corresponding rows were also deleted from another table. This is CORRECT. The matter of the fact, there is no error or anything and SQL Server is behaving how it should be behaving. The problem was in the understanding and inappropriate implementations of business logic.  What they needed was Product Master Table, Current Product Catalogue, and Product Order Details History tables. However, they were using only two tables and without proper understanding the relation between them was build using foreign keys. If there were only two table, they should have used soft delete which will not actually delete the record but just hide it from the original product table. This workaround could have got them saved from cascading delete issues. I will be writing a detailed post on the design implications etc in my future post as in above three lines I cannot cover every issue related to designing and it is also not the scope of the blog post. More about designing in future blog posts. Once they learn their mistake, they were happy as there was no intrusion but trust me sometime we are our own enemy and this is a great example of it. In tomorrow’s blog post we will go over their code and workarounds. Feel free to share your opinions, experiences and comments. 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 – A Brief Note on SET TEXTSIZE

    - by pinaldave
    Here is a small conversation I received. I thought though an old topic, indeed a thought provoking for the moment. Question: Is there any difference between LEFT function and SET TEXTSIZE? I really like this small but interesting question. The question does not specify the difference between usage or performance. Anyway we will quickly take a look at how TEXTSIZE works. You can run the following script to see how LEFT and SET TEXTSIZE works. USE TempDB GO -- Create TestTable CREATE TABLE MyTable (ID INT, MyText VARCHAR(MAX)) GO INSERT MyTable (ID, MyText) VALUES(1, REPLICATE('1234567890', 100)) GO -- Select Data SELECT ID, MyText FROM MyTable GO -- Using Left SELECT ID, LEFT(MyText, 10) MyText FROM MyTable GO -- Set TextSize SET TEXTSIZE 10; SELECT ID, MyText FROM MyTable; SET TEXTSIZE 2147483647 GO -- Clean up DROP TABLE MyTable GO Now let us see the usage result which we receive from both of the example. If you are going to ask what you should do – I really do not know. I can tell you where I will use either of the same. LEFT seems to be easy to use but again if you like to do extra work related to SET TEXTSIZE go for it. Here is how I will use SET TEXTSIZE. If I am selecting data from in my SSMS for testing or any other non production related work from a large table which has lots of columns with varchar data, I will consider using this statement to reduce the amount of the data which is retrieved in the result set. In simple word, for testing purpose I will use it. On the production server, there should be a specific reason to use the same. Here is my candid opinion – I do not think they can be directly comparable even though both of them give the exact same result. LEFT is applicable only on the column of a single SELECT statement. where it is used but it SET TEXTSIZE applies to all the columns in the SELECT and follow up SELECT statements till the SET TEXTSIZE is not modified again in the session. Uncomparable! I hope this sample example gives you idea how to use SET TEXTSIZE in your daily use. I would like to know your opinion about how and when do you use this feature. Please leave a comment. 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 – Fix: Error: 10920 Cannot drop user-defined function. It is being used as a resource governor classifier

    - by pinaldave
    If you have not read my SQL SERVER – Simple Example to Configure Resource Governor – Introduction to Resource Governor yesterday’s detailed primer on Resource Governor, I suggest you go ahead and read it before continuing this article. After reading the article the very first email I received was as follows: “Pinal, I configured resource governor on my development server and it worked fine with tests I ran. After doing some tests, I decided to remove the resource governor and as a first step I disabled it however, I was not able to drop the classification function during the process of the clean up. It was continuously giving me following error. Msg 10920, Level 16, State 1, Line 1 Cannot drop user-defined function myudfname. It is being used as a resource governor classifier. Would you please give me solution?” The original email was really this short and there is no other information. I am glad he has done experiments on development server and not on the production server. Production server must not be the playground of the experiments. I think I have covered the answer of this error in an earlier blog post. If the user disables the Resource Governor it is still not possible to drop the function because it can be enabled again and when enabled it can still use the same function. Here is the simple resolution of the how one can drop the classifier function (do this only if you are not going to use the function). The reason the classifier function can’t be dropped because it is associated with resource governor. Create a new classified function for your resource governor or just assign NULL as described in the following T-SQL Script and you will be able to drop the function without error. ALTER RESOURCE GOVERNOR WITH (CLASSIFIER_FUNCTION = NULL) GO ALTER RESOURCE GOVERNOR DISABLE GO DROP FUNCTION dbo.UDFClassifier GO I am glad that user asked me question instead of doing something radically different, which can leave the server in the unusable state. I am aware of this only method to avoid this error. Is there any better way to achieve the same? 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 – Windows Azure Training Kit Updated October 2012

    - by pinaldave
    Microsoft has recently released the updated to Windows Azure Training Kit. Earlier this month they have updated the kit and included quite a lot of things. Now the training kit contains 47 hands-on labs, 24 demos and 38 presentations. The best part is that the kit is now available to download in two different formats 1) Full Package (324.5 MB) and 2) Web Installer (2.4 MB). The full package enables you to download all of the hands-on labs and presentations to your local machine. The Web Installer allows you to select and download just the specific hands-on labs and presentations that you need. This Windows Azure Training Kit contains Hands on Labs, Presentations and Videos and Demos. I encourage all of you to try this out as well. The Kit also contains details about Samples and Tools. The training kit is the most authoritative learning resource on Windows Azure. You can download the Windows Azure Training Kit from here. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Azure, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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