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• SQL SERVER – NTFS File System Performance for SQL Server

  - by pinaldave

  Note: Before practicing any of the suggestion of this article, consult your IT Infrastructural Admin, applying the suggestion without proper testing can only damage your system. Question: “Pinal, we have 80 GB of data including all the database files, we have our data in NTFS file system. We have proper backups are set up. Any suggestion for our NTFS file system performance improvement. Our SQL Server box is running only SQL Server and nothing else. Please advise.” When I receive questions which I have just listed above, it often sends me deep thought. Honestly, I know a lot but there are plenty of things, I believe can be built with community knowledge base. Today I need you to help me to complete this list. I will start the list and you help me complete it. NTFS File System Performance Best Practices for SQL Server Disable Indexing on disk volumes Disable generation of 8.3 names (command: FSUTIL BEHAVIOR SET DISABLE8DOT3 1) Disable last file access time tracking (command: FSUTIL BEHAVIOR SET DISABLELASTACCESS 1) Keep some space empty (let us say 15% for reference) on drive is possible (Only on Filestream Data storage volume) Defragement the volume Add your suggestions here… The one which I often get a pretty big debate is NTFS allocation size. I have seen that on the disk volume which stores filestream data, when increased allocation to 64K from 4K, it reduces the fragmentation. Again, I suggest you attempt this after proper testing on your server. Every system is different and the file stored is different. Here is when I would like to request you to share your experience with related to NTFS allocation size. If you do not agree with any of the above suggestions, leave a comment with reference and I will modify it. Please note that above list prepared assuming the SQL Server application is only running on the computer system. The next question does all these still relevant for SSD – I personally have no experience with SSD with large database so I will refrain from comment. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Transaction Log Full – Transaction Log Larger than Data File – Notes from Fields #001

  - by Pinal Dave

  I am very excited to announce a new series on this blog – Notes from Fields. I have been blogging for almost 7 years on this blog and it has been a wonderful experience. Though, I have extensive experience with SQL and Databases, it is always a good idea that we consult experts for their advice and opinion. Following the same thought process, I have started this new series of Notes from Fields. In this series we will have notes from various experts in the database world. My friends at Linchpin People have graciously decided to support me in my new initiation.  Linchpin People are database coaches and wellness experts for a data driven world. In this very first episode of the Notes from Fields series database expert Tim Radney (partner at Linchpin People) explains a very common issue DBA and Developer faces in their career, when database logs fills up your hard-drive or your database log is larger than your data file. Read the experience of Tim in his own words. As a consultant, I encounter a number of common issues with clients.  One of the more common things I encounter is finding a user database in the FULL recovery model that does not make a regular transaction log backups or ever had a transaction log backup. When I find this, usually the transaction log is several times larger than the data file. Finding this issue is very significant to me in that it allows to me to discuss service level agreements with the client. I get to ask questions such as, are nightly full backups sufficient or do they need point in time recovery.  This conversation has now signed with the customer and gets them to thinking about their disaster recovery and high availability solutions. This issue is also very prominent on SQL Server forums and usually has the title of “Help, my transaction log has filled up my disk” or “Help, my transaction log is many times the size of my database”. In cases where the client only needs the previous full nights backup, I am able to change the recovery model to SIMPLE and shrink the transaction log using DBCC SHRINKFILE (2,1) or by specifying the transaction log file name by using DBCC SHRINKFILE (file_name, target_size). When the client needs point in time recovery then in most cases I will still end up switching the client to the SIMPLE recovery model to truncate the transaction log followed by a full backup. I will then schedule a SQL Agent job to make the regular transaction log backups with an interval determined by the client to meet their service level agreements. It should also be noted that typically when I find an overgrown transaction log the virtual log file count is also out of control. I clean up will always take that into account as well.  That is a subject for a future blog post. If your SQL Server is facing any issue we can Fix Your SQL Server. Additional reading: Monitoring SQL Server Database Transaction Log Space Growth – DBCC SQLPERF(logspace)  SQL SERVER – How to Stop Growing Log File Too Big Shrinking Truncate Log File – Log Full Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – CSVExpress and Quick Data Load

  - by pinaldave

  One of the newest ETL tools is CSVexpress.com.  This is a program that can quickly load any CSV file into ODBC compliant databases uses data integration.  For those of you familiar with databases and how they operate, the question that comes to mind might be what use this program will have in your life. I have written earlier article on this subject over here SQL SERVER – Import CSV into Database – Transferring File Content into a Database Table using CSVexpress. You might know that RDBMS have automatic support for loading CSV files into tables – but it is not quite as easy as one click of a button.  First of all, most databases have a command line interface and you need the file and configuration script in order to load up.  You also need to know enough to write the script – which for novices can be extremely daunting.  On top of all this, if you work with more than one type of RDBMS, you need to know the ins and outs of uploading and writing script for more than one program. So you might begin to see how useful CSVexpress.com might be!  There are many other tools that enable uploading files to a database.  They can be very fancy – some can generate configuration files automatically, others load the data directly.  Again, novices will be able to tell you why these aren’t the most useful programs in the world.  You see, these programs were created with SQL in mind, not for uploading data.  If you don’t have large amounts of data to upload, getting the configurations right can be a long process and you will have to check the code that is generated yourself.  Not exactly “easy to use” for novices. That makes CSVexpress.com one of the best new tools available for everyone – but especially people who don’t want to learn a lot of new material all at once.  CSVexpress has an easy to navigate graphical user interface and no scripting or coding is required.  There are built-in constraints and data validations, and you can configure transforms and reject records right there on the screen.  But the best thing of all – it’s free! That’s right, you can download CSVexpress for free from www.csvexpress.com and start easily uploading and configuring riles almost immediately.  If you’re currently happy with your method of data configuration, keep up with the good work.  For the rest of us, there’s CSVexpress.com. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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• SQL SERVER – Quiz and Video – Introduction to Basics of a Query Hint

  - by pinaldave

  This blog post is inspired from SQL Architecture Basics Joes 2 Pros: Core Architecture concepts – SQL Exam Prep Series 70-433 – Volume 3. [Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to Basics of a Query Hint – A Primer. In the article we discussed various basics terminology of the query hints. The article further covers following important concepts of query hints. Expecting Seek and getting a Scan Creating an index for improved optimization Implementing the query hint Above three are the most important concepts related to query hint 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) You have the following query: DECLARE @UlaChoice TinyInt SET @Type = 1 SELECT * FROM LegalActivity WHERE UlaChoice = @UlaChoice You have a nonclustered index named IX_Legal_Ula on the UlaChoice field. The Primary key is on the ID field and called PK_Legal_ID 99% of the time the value of the @UlaChoice is set to ‘YP101′. What query will achieve the best optimization for this query? SELECT * FROM LegalActivity WHERE UlaChoice = @UlaChoice WITH(INDEX(X_Legal_Ula)) SELECT * FROM LegalActivity WHERE UlaChoice = @UlaChoice WITH(INDEX(PK_Legal_ID)) SELECT * FROM LegalActivity WHERE UlaChoice = @UlaChoice OPTION (Optimize FOR(@UlaChoice = ‘YP101′)) 2) You have the following query: SELECT * FROM CurrentProducts WHERE ShortName = ‘Yoga Trip’ You have a nonclustered index on the ShortName field and the query runs an efficient index seek. You change your query to use a variable for ShortName and now you are using a slow index scan. What query hint can you use to get the same execution time as before? WITH LOCK FAST OPTIMIZE FOR MAXDOP READONLY 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) 3 2) 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 – Difference Between CURRENT_TIMESTAMP and GETDATE() – CURRENT_TIMESTAMP Equivalent in SQL Server

  - by pinaldave

  A common question – I often get from Oracle/MySQL Professionals: “What is the Equivalent to CURRENT_TIMESTAMP in SQL Server?” Here is a common question I often get from SQL Server Professionals: “What are differences between Difference Between CURRENT_TIMESTAMP and GETDATE ()?” Very simple question but have showed up so frequently that I feel like to write about it. Well in SQL Server GETDATE() is Equivalent to CURRENT_TIMESTAMP. However, if you use CURRENT_TIMESTAMP in your select statement it will work fine. You can see in the above example – both of them returns the same value. Now let us go to next question regarding difference between GETDATE and CURRENT_TIMESTAMP. Well, the matter of the fact, there is no difference between them in SQL Server (Reference Link). CURRENT_TIMESTAMP is an ANSI SQL function, whereas GETDATE is T-SQL implementation of the same function. Both of them derive value from the operating system of the computer on which SQL Server instance is running. Above discussion prompts another question – in this case, what should one use GETDATE or CURRENT_TIMESTAMP? Well, this is indeed tricky and interesting question. I think I am very comfortable using the GETDATE () so I will go to use it but a matter of the fact there is no right or wrong answer. If you want to follow ancient saying “When in Rome, do as the Romans do”, I suggest using the GETDATE (), or continue using CURRENT_TIMESTAMP. With that said, there is one very important property we all need to keep in mind. If you use CURRENT_TIMESTAMP while creating an object, they are automatically converted to GETDATE() and stored internally. To illustrate what I am suggesting here is the example - Create a table using the following script CREATE TABLE [dbo].[TestTable]( [Cold2] [datetime] NULL ) ON [PRIMARY] GO ALTER TABLE [dbo].[TestTable] ADD DEFAULT (CURRENT_TIMESTAMP) FOR [Cold2] GO Now go to SSMS and generate the script for the table and you will notice following syntax. CREATE TABLE [dbo].[TestTable]( [Cold2] [datetime] NULL ) ON [PRIMARY] GO ALTER TABLE [dbo].[TestTable] ADD DEFAULT (GETDATE()) FOR [Cold2] GO You can notice that SQL Server have automatically converted CURRENT_TIMESTAMP to GETDATE(). I guess this gives us an idea how they behave. Now go ahead and make your choice! Do let me know which one will you use CURRENT_TIMESTAMP or GETDATE () in the comments area. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQLAuthority News – Presented Soft Skill Session on Presentation Skills at SQL Bangalore on May 3, 2014

  - by Pinal Dave

  I have presented on various database technologies for almost 10 years now. SQL, Database and NoSQL have been part of my life. Earlier this month, I had the opportunity to present on the topic Performing an Effective Presentation. I must say it was blast to prepare as well as present this session. This event was part of the SQL Bangalore community. If you are in Bangalore, you must be part of this group. SQL Bangalore is a wonderful community and we always have a great response when we present on technology. It is SQL User Group and we discuss everything SQL there. This month we had SQL Server 2014 theme and we had a community launch of SQL Server. We have the best of the best speakers presenting on SQL Server 2014 technology. The event had amazing speakers and each of them did justice to the subject. You can read about this over here. In this session I told a story from my life. I talked about who inspired me and how I learned to speak in public. I told stories about two legends  who have inspired me. There is no video recording of this session. If you want to get resources from this session, please sign up my newsletter at http://bit.ly/sqllearn. Well, I had a great time at this event. We had over 250 people showed up at this event and had a grand  time together. I personally enjoyed a session of Amit Benerjee, Balmukund Lakhani and Vinod Kumar. Ken and Surabh also entertained the audience. Overall, this was a grand event and if you were in Bangalore and did not make it to this event. You did miss out on a few things. Here are a few photos of this event. SQL Bangalore UG Nupur, Chandra, Shaivi, Balmukund, Amit, Vinod [captions This] SQL Bangalore UG Audience Pinal Dave presenting at SQL UG in Bangalore Here are few of the slides from this presentation: Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, T SQL

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• SQLAuthority News – Updates on Contests, Books and SQL Server

  - by pinaldave

  There are lots of things happening on this blog and I feel sometime it is difficult to keep up. One of the suggestion I keep on receiving if there is a single page where one can visit and know the updates. I did consider of the same at some point but in era of RSS Feed it is difficult to have proper audience to that page. Here are few updates on various contest and books give away in recent time. Combo set of 5 Joes 2 Pros Book – 1 for YOU and 1 for Friend – I have received so many entries for this contest. Many have sent me email asking if this contest can be extended by couple of days. For the same the deadline for this contest is now Nov 10th 7 AM. You can send your entries by that time. The prize is 2 combo set of Joes 2 Pros is of USD 444. If you have not take part in the contest please take part now. Guess What is in the box? – There were many entry for this contest. We played this contest on blog as well, facebook. The answer of this contest was announced in 2 days in blog post announcing my new book. The winner was Manas Dash from Bangalore. He answered “The box will contain SQL book authored by Vinod and Pinal”. This was the closest answer we received. Win 5 SQL Programming Book Contest will have winner announced by Nov 15th and winners will be sent email. Win 5 SQL Wait Stats Book Contest is closed and winners have been sent their award. My third book SQL Server Interview Questions and Answers have run out of stock in India in 36 hours of its launch. We are working very hard to make it available again. Thank you again for excellent support! Without your participation all the give away have no significance. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQLAuthority News – Weekend Experiment with NuoDB – Points to Pondor and Whitepaper

  - by pinaldave

  This weekend I have downloaded the latest beta version of NuoDB. I found it much improved and better UI. I was very much impressed as the installation was very smooth and I was up and running in less than 5 minutes with the product. The tools which are related to the Administration of the NuoDB seems to get makeover during this beta release. As per the claim they support now Solaris platform and have improved the native MacOS installation. I neither have Mac nor Solaris – I wish I would have experimented with the same. I will appreciate if anyone out there can confirm how the installations goes on these platforms. I have previously blogged about my experiment with NuoDB here: SQL SERVER – Weekend Project – Experimenting with ACID Transactions, SQL Compliant, Elastically Scalable Database SQL SERVER – Beginning NuoDB – Who will Benefit and How to Start SQL SERVER – Follow up on Beginning NuoDB – Who will Benefit and How to Start – Part 2 I am very impressed with the product so far and I have decided to understand the product further deep. Here are few of the questions which I am going to try to find answers with regards to NuoDB. Just so it is clear – NuoDB is not NOSQL, matter of the fact, it is following all the ACID properties of the database. If ACID properties are crucial why many NoSQL products are not adhering to it? (There are few out there do follow ACID but not all). I do understand the scalability of the database however does elasticity is crucial for the database and if yes how? (Elasticity is where the workload on the database is heavily fluctuating and the need of more than a single database server is coming up). How NuoDB has built scalable, elastic and 100% ACID compliance database which supports multiple platforms? How is NOSQL compared to NuoDB’s new architecture? In the next coming weeks, I am going to explore above concepts and dive deeper into the understanding of the same. Meanwhile I have read following white paper written by Experts at University of California at Santa Barbara. Very interesting read and great starter on the subject Database Scalability, Elasticity, and Autonomy in the Cloud. Additionally, my questions are also talking about NoSQL, this weekend I have started to learn about NoSQL from Pluralsight‘s online learning library. I will share my experience very soon. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL White Papers, T SQL, Technology Tagged: NuoDB

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• SQL SERVER – How to Force New Cardinality Estimation or Old Cardinality Estimation

  - by Pinal Dave

  After reading my initial two blog posts on New Cardinality Estimation, I received quite a few questions. Once I receive this question, I felt I should have clarified it earlier few things when I started to write about cardinality. Before continuing this blog, if you have not read it before I suggest you read following two blog posts. SQL SERVER – Simple Demo of New Cardinality Estimation Features of SQL Server 2014 SQL SERVER – Cardinality Estimation and Performance – SQL in Sixty Seconds #072 Q: Does new cardinality will improve performance of all of my queries? A: Remember, there is no 0 or 1 logic when it is about estimation. The general assumption is that most of the queries will be benefited by new cardinality estimation introduced in SQL Server 2014. That is why the generic advice is to set the compatibility level of the database to 120, which is for SQL Server 2014. Q: Is it possible that after changing cardinality estimation to new logic by setting the value to compatibility level to 120, I get degraded performance for few queries? A: Yes, it is possible. However, the number of the queries where this impact should be very less. Q: Can I still run my database in older compatibility level and force few queries to newer cardinality estimation logic? If yes, How? A: Yes, you can do that. You will need to force your query with trace flag 2312 to use newer cardinality estimation logic. USE AdventureWorks2014 GO -- Old Cardinality Estimation ALTER DATABASE AdventureWorks2014 SET COMPATIBILITY_LEVEL = 110 GO -- Using New Cardinality Estimation SELECT [AddressID],[AddressLine1],[City] FROM [Person].[Address] OPTION(QUERYTRACEON 2312);; -- Using Old Cardinality Estimation SELECT [AddressID],[AddressLine1],[City] FROM [Person].[Address]; GO Q: Can I run my database in newer compatibility level and force few queries to older cardinality estimation logic? If yes, How? A: Yes, you can do that. You will need to force your query with trace flag 9481 to use newer cardinality estimation logic. USE AdventureWorks2014 GO -- NEW Cardinality Estimation ALTER DATABASE AdventureWorks2014 SET COMPATIBILITY_LEVEL = 120 GO -- Using New Cardinality Estimation SELECT [AddressID],[AddressLine1],[City] FROM [Person].[Address]; -- Using Old Cardinality Estimation SELECT [AddressID],[AddressLine1],[City] FROM [Person].[Address] OPTION(QUERYTRACEON 9481); GO I guess, I have covered most of the questions so far I have received. If I have missed any questions, please send me again and I will include the same. 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 – Quiz and Video – Introduction to SQL Error Actions

  - by pinaldave

  This blog post is inspired from SQL Programming Joes 2 Pros: Programming and Development for Microsoft SQL Server 2008 – SQL Exam Prep Series 70-433 – Volume 4. [Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to SQL Error Actions – A Primer. In the article we discussed various basics terminology of the error handling. The article further covers following important concepts of error handling. Introduction to SQL Error Actions Statement Termination Scope Abortion Batch Termination Above three are the most important concepts related to error handling 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 SQL Server error action happens for errors with a severity of 11-16 when you set the XACT_ABORT setting to ON? You will get Statement Termination. You will get Scope Abortion. You will get Batch Abortion. You will get Connection Termination. SQL Server will pick the error action. 2.) Which SQL Server error action happens for errors with a severity of 11-16 when you set the XACT_ABORT setting to OFF? You will get Statement Termination You will get Scope Abortion You will get Batch Abortion You will get Connection Termination SQL Server will pick the error action 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) 3 2) 5 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 – Simple Explanation and Puzzle with SOUNDEX Function and DIFFERENCE Function

  - by pinaldave

  Earlier this week I asked a question where I asked how to Swap Values of the column without using CASE Statement. Read here: A Puzzle – Swap Value of Column Without Case Statement,there were more than 50 solutions proposed in the comment. There were many creative solutions. I have mentioned my personal favorite (different ones) here: Solution of Puzzle – Swap Value of Column Without Case Statement. However, I received lots of questions regarding one of the Solution by SIJIN KUMAR V P. He has used the function SOUNDEX in his solution. The request was to explain how SOUNDEX and DIFFERENCE works. Well, there are pretty decent documentations provided over here SOUNDEX function and DIFFERENCE over on MSDN and if I attempt to explain this function I will end up writing the same details which are available on MSDN. Instead of writing theory, we will try to learn this function by using a couple of simple puzzles. You try to solve the puzzles using the MSDN and see if you can learn something very quickly. In simple words - SOUNDEX converts an alphanumeric string to a four-character code to find similar-sounding words or names. The first character of the code is the first character of character_expression and the second through fourth characters of the code are numbers that represent the letters in the expression. Vowels incharacter_expression are ignored unless they are the first letter of the string. DIFFERENCE function returns an integer value. The  integer returned is the number of characters in the SOUNDEX values that are the same. The return value ranges from 0 through 4: 0 indicates weak or no similarity, and 4 indicates strong similarity or the same values. Learning Puzzle 1: Now let us run following four queries and observe its output. SELECT SOUNDEX('SQLAuthority') SdxValue SELECT SOUNDEX('SLTR') SdxValue SELECT SOUNDEX('SaLaTaRa') SdxValue SELECT SOUNDEX('SaLaTaRaM') SdxValue When you look at the result set all the four values are same. The reason for all the values to be same is as for SQL Server SOUNDEX function all the four strings are similarly sounding string. Learning Puzzle 2: Now let us run following five queries and observe its output. SELECT DIFFERENCE (SOUNDEX('SLTR'),SOUNDEX('SQLAuthority')) SELECT DIFFERENCE (SOUNDEX('TH'),SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SQLAuthority',SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SLTR',SOUNDEX('SQLAuthority')) SELECT DIFFERENCE ('SLTR','SQLAuthority') When you look at the result set you will get the result in the ranges from 1 to 4. Here is how it works if your result is 0 which means absolutely not relevant to each other and if your result is 1 which means the results are relevant to each other. Have you ever used above two functions in your business need or on production server? If yes, would you please leave a comment with use cases. I believe it will be beneficial to everyone. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Iridium I/O – SQL Server Deduplication that Shrinks Databases and Improves Performance

  - by Pinal Dave

  Database performance is a common problem for SQL Server DBA’s.  It seems like we spend more time on performance than just about anything else.  In many cases, we use scripts or tools that point out performance bottlenecks but we don’t have any way to fix them.  For example, what do you do when you need to speed up a query that is already tuned as well as possible?  Or what do you do when you aren’t allowed to make changes for a database supporting a purchased application? Iridium I/O for SQL Server was originally built at Confio software (makers of Ignite) because DBA’s kept asking for a way to actually fix performance instead of just pointing out performance problems. The technology is certified by Microsoft and was so promising that it was spun out into a separate company that is now run by the Confio Founder/CEO and technology management team. Iridium uses deduplication technology to both shrink the databases as well as boost IO performance.  It is intriguing to see it work.  It will deduplicate a live database as it is running transactions.  You can watch the database get smaller while user queries are running. Iridium is a simple tool to use. After installing the software, you click an “Analyze” button which will spend a minute or two on each database and estimate both your storage and performance savings.  Next, you click an “Activate” button to turn on Iridium I/O for your selected databases.  You don’t need to reboot the operating system or restart the database during any part of the process. As part of my test, I also wanted to see if there would be an impact on my databases when Iridium was removed.  The ‘revert’ process (bringing the files back to their SQL Server native format) was executed by a simple click of a button, and completed while the databases were available for normal processing. I was impressed and enjoyed playing with the software and encourage all of you to try it out.  Here is the link to the website to download Iridium for free. . Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Creating All New Database with Full Recovery Model

  - by pinaldave

  Sometimes, complex problems have very simple solutions. Let us see the following email which I received recently. “Hi Pinal, In our system when we create new database, by default, they are all created with the Simple Recovery Model. We have to manually change the recovery model after we create the database. We used the following simple T-SQL code: CREATE DATABASE dbname. We are very frustrated with this situation. We want all our databases to have the Full Recovery Model option by default. We are considering the following methods; please suggest the most efficient one among them. 1) Creating a Policy; when it is violated, the database model can be fixed 2) Triggers at Server Level 3) Automated Job which goes through all the databases and checks their recovery model; if the DBA has not changed the model, then the job will list the Databases and change their recovery model Also, we have a situation where we need a database in the Simple Recovery Model as well – how to white list them? Please suggest the best method.” Indeed, an interesting email! The answer to their question, i.e., which is the best method to fit their needs (white list, default, etc)? It will be NONE of the above. Here is the solution in one line and also the easiest way: Just go to your Model database: Path in SSMS >> Databases > System Databases >> model >> Right Click Properties >> Options >> Recovery Model - Select Full from dropdown. Every newly created database takes its base template from the Model Database. If you create a custom SP in the Model Database, when you create a new database, it will automatically exist in that database. Any database that was already created before making changes in the Model Database will not be affected at all. Creating Policy is also a good method, and I will blog about this in a separate blog post, but looking at current specifications of the reader, I think the Model Database should be modified to have a Full Recovery Option. While writing this blog post, I remembered my another blog post where the model database log file was growing drastically even though there were no transactions SQL SERVER – Log File Growing for Model Database – model Database Log File Grew Too Big. NOTE: Please do not touch the Model Database unnecessary. It is a strict “No.” If you want to create an object that you need in all the databases, then instead of creating it in model database, I suggest that you create a new database called maintenance and create the object there. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Question, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – A Puzzle Part 3 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value

  - by pinaldave

  Before continuing this blog post – please read the two part of the SEQUENCE Puzzle here A Puzzle – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value and A Puzzle Part 2 – Fun with SEQUENCE in SQL Server 2012 – Guess the Next Value Where we played a simple guessing game about predicting next value. The answers the of puzzle is shared on the blog posts as a comment. Now here is the next puzzle based on yesterday’s puzzle. I recently shared the puzzle of the blog post on local user group and it was appreciated by attendees. First execute the script which I have written here. Today’s script is bit different than yesterday’s script as well it will require you to do some service related activities. I suggest you try this on your personal computer’s test environment when no one is working on it. Do not attempt this on production server as it will for sure get you in trouble. The purpose to learn how sequence behave during the unexpected shutdowns and services restarts. Now guess what will be the next value as requested in the query. USE AdventureWorks2012 GO -- Create sequence CREATE SEQUENCE dbo.SequenceID AS BIGINT START WITH 1 INCREMENT BY 1 MINVALUE 1 MAXVALUE 500 CYCLE CACHE 100; GO -- Following will return 1 SELECT next value FOR dbo.SequenceID; ------------------------------------- -- simulate server crash by restarting service -- do not attempt this on production or any server in use ------------------------------------ -- Following will return ??? SELECT next value FOR dbo.SequenceID; -- Clean up DROP SEQUENCE dbo.SequenceID; GO Once the server is restarted what will be the next value for SequenceID. We can learn interesting trivia’s about this new feature of SQL Server using this puzzle. Hint: Pay special attention to the difference between new number and earlier number. Can you see the same number in the definition of the CREATE SEQUENCE? Bonus Question: How to avoid the behavior demonstrated in above mentioned query. Does it have any effect of performance? I suggest you try to attempt to answer this question without running this code in SQL Server 2012. You can restart SQL Server using command prompt as well. I will follow up of the answer in comments below. Recently my friend Vinod Kumar wrote excellent blog post on SQL Server 2012: Using SEQUENCE, you can head over there for learning sequence in details. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL Contests – Solution – Identify the Database Celebrity

  - by Pinal Dave

  Last week we were running contest Identify the Database Celebrity and we had received a fantastic response to the contest. Thank you to the kind folks at NuoDB as they had offered two USD 100 Amazon Gift Cards to the winners of the contest. We had also additional contest that users have to download and install NuoDB and identified the sample database. You can read about the contest over here. Here is the answer to the questions which we had asked earlier in the contest. Part 1: Identify Database Celebrity Personality 1 – Edgar Frank “Ted” Codd (August 19, 1923 – April 18, 2003) was an English computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He made other valuable contributions to computer science, but the relational model, a very influential general theory of data management, remains his most mentioned achievement. (Wki) Personality 2 – James Nicholas “Jim” Gray (born January 12, 1944; lost at sea January 28, 2007; declared deceased May 16, 2012) was an American computer scientist who received the Turing Award in 1998 “for seminal contributions to database and transaction processing research and technical leadership in system implementation.” (Wiki) Personality 3 – Jim Starkey (born January 6, 1949 in Illinois) is a database architect responsible for developing InterBase, the first relational database to support multi-versioning, the blob column type, type event alerts, arrays and triggers. Starkey is the founder of several companies, including the web application development and database tool company Netfrastructure and NuoDB. (Wiki) Part 2: Identify NuoDB Samples Database Names In this part of the contest one has to Download NuoDB and install the sample database Hockey. Hockey is sample database and contains few tables. Users have to install sample database and inform the name of the sample databases. Here is the valid answer. HOCKEY PLAYERS SCORING TEAM Once again, it was indeed fun to run this contest. I have received great feedback about it and lots of people wants me to run similar contest in future. I promise to run similar interesting contests in the near future. Winners Within next two days, we will let winners send emails. Winners will have to confirm their email address and NuoDB team will send them directly Amazon Cards. Once again it was indeed fun to run this contest. 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 – Working with FileTables in SQL Server 2012 – Part 2 – Methods to Insert Data Into Table

  - by pinaldave

  Read Part 1 Working with FileTables in SQL Server 2012 – Part 1 – Setting Up Environment In this second part of the series, we will see how we can insert the files into the FileTables. There are two methods to insert the data into FileTables: Method 1: Copy Paste data into the FileTables folder First, find the folder where FileTable will be storing the files. Go to Databases >> Newly Created Database (FileTableDB) >> Expand Tables. Here you will see a new folder which says “FileTables”. When expanded, it gives the name of the newly created “FileTableTb”. Right click on the newly created table, and click on “Explore FileTable Directory”. This will open up the folder where the FileTable data will be stored. When clicked on the option it will open up following folder in my local machine where the FileTable data will be stored. \\127.0.0.1\mssqlserver\FileTableDB\FileTableTb_Dir You can just copy your document just there. I copied few word document there and ran select statement to see the result. USE [FileTableDB] GO SELECT * FROM FileTableTb GO SELECT * returns all the rows. Here is SELECT statement which has only few columns selected from FileTable. SELECT [name] ,[file_type] ,CAST([file_stream] AS VARCHAR) FileContent ,[cached_file_size] ,[creation_time] ,[last_write_time] ,[last_access_time] FROM [dbo].[FileTableTb] GO I believe this is the simplest method to populate FileTable, because you just have to move the files to the specific table. Method 2: T-SQL Insert Statement There are always cases when you might want to programmatically insert the images into SQL Server File table. Here is a quick method which you can use to insert the data in the file table. I have inserted a very small text file using T-SQL, and later on, reading that using SELECT statement demonstrated in method 1 above. INSERT INTO [dbo].[FileTableTb] ([name],[file_stream]) SELECT 'NewFile.txt', * FROM OPENROWSET(BULK N'd:\NewFile.txt', SINGLE_BLOB) AS FileData GO The above T-SQL statement will copy the NewFile.txt to new location. When you run SELECT statement, it will retrieve the file and list in the resultset. Additionally, it returns the content in the SELECT statement as well. I think it is a pretty interesting way to insert the data into the FileTable. SELECT [name] ,[file_type] ,CAST([file_stream] AS VARCHAR) FileContent ,[cached_file_size] ,[creation_time] ,[last_write_time] ,[last_access_time] FROM [dbo].[FileTableTb] GO There are more to FileTable and we will see those in my future blog posts. 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: Filestream

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• SQLAuthority News – 5th Anniversary Giveaways

  - by pinaldave

  Please read my 5th Anniversary post and my quick note on history of the Database. I am sure that we all have friends and we value friendship more than anything. In fact, the complete model of Facebook is built on friends. If you have lots of friends, you must be a lucky person. Having a lot of friends is indeed a good thing. I consider all you blog readers as my friends so now I want do something for you. What is it? Well, send me details about how many of your friends like my page and you would have a chance to win lots of learning materials for yourself and your friends. Here are the exciting prizes awaiting the lucky winner: Combo set of 5 Joes 2 Pros Book – 1 for YOU and 1 for Friend This is USD 444 (each set USD 222) worth gift. It contains all the five Joes 2 Pros books (Vol1, Vol2, Vol3, Vol4, Vol5) + 1 Learning DVD. [Amazon] | [Flipkart] If in case you submitted an entry but didn’t win the Combo set of 5 Joes 2 Pros books, you could still will  my SQL Server Wait Stats book as a consolation prize! I will pick the next 5 participants who have the highest number of friends who “liked” the Facebook page, http://facebook.com/SQLAuth. Instead of sending one copy, I will send you 2 copies so you can share one copy with a friend of yours. Well, it is important to share our learning and love with friends, isn’t it? Note: Just take a screenshot of http://facebook.com/SQLAuth using Print Screen function and send it by Nov 7th to pinal ‘at’ sqlauthority.com.. There are no special freebies to early birds so take your time and see if you can increase your friends like count by Nov 7th. Guess – What is in it? It is quite possible you are not a Facebook or Twitter user. In that case you can still win a surprise from me. You have 2 days to guess what is in this box. If you guess it correct and you are one of the first 5 persons to have the correct answer – you will get what is in this box for free. Please note that you have only 48 hours to guess. Please give me your guess by commenting to this blog post. Reference:  Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Milestone, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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• SQLAuthority News – SQL Server Wait Stats – eBook to Download on Kindle – Answer to FREE PDF Download Request

  - by pinaldave

  Being a book author is a completely new experience for me. I am yet to come across the issues faced by expert book authors. I assume that these interesting issues can be routine ones for expert book authors. One of the biggest requests I am getting for my SQL Server Wait Stats [Amazon] | [Flipkart] | [Kindle] book is my humble attempt to write a book. This is our very first experiment, and the book is beginning of the subject of SQL Server Wait Stats; we will come up with a new version of the book later next year when we have enough information for the SQL Server 2012 version. Following are the top 2 requests that I keep on receiving in emails, on blogs, Twitter, and Facebook. “Please send us FREE PDF of your book so we do not have to purchase it.” “If you can share with us the eBook (free and downloadable) format of your book, we will share it with everybody we know and you will get additional exposure.” Here is my response for the abovementioned requests: If you really need my book and cannot purchase it due to financial trouble, then feel free to let me know and I will purchase it myself and ship it to you. If you are in a country where the print book not available, then you can buy the Kindle book, which is available online in any country, and you can just read it on your computer and mobile devices. You DO NOT have to own a Kindle to read a Kindle format book. You can freely download Kindle software on your desired format and purchase the book online. For next 5 days, the kindle book is available at 3.99 in USA, and in other countries, the price is anywhere between 3.99 and 5.99. The price will go up by USD 2 everywhere across the world after 1st November, 2011. Here is the link to download Kindle Software for free PC, WP7, and in marketplace for various other mobile devices. I thank you for giving warm response to SQL Server Wait Stats book. I am motivated to write the next expanded version of this book. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – BI Quiz Hint – Performance Tuning Cubes – Hints

  - by pinaldave

  I earlier wrote about SQL BI Quiz over here and here. The details of the quiz is here: Working with huge data is very common when it is about Data Warehousing. It is necessary to create Cubes on the data to make it meaningful and consumable. There are cases when retrieving the data from cube takes lots of the time. Let us assume that your cube is returning you data very quickly. Suddenly on one day it is returning the data very slowly. What are the three things will you to diagnose this. After diagnose what you will do to resolve performance issue. Participate in my question over here I required BI Expert Jason Thomas to help with few hints to blog readers. He is one of the leading SSAS expert and writes a complicated subject in simple words. If queries were executing properly before but now take a long time to return the data, it means that there has been a change in the environment in which it is running. Some possible changes are listed below:-  1) Data factors:- Compare the data size then and now. Increase in data can result in different execution times. Poorly written queries as well as poor design will not start showing issues till the data grows. How to find it out? (Ans : SQL Server profiler and Perfmon Counters can be used for identifying the issues and performance  tuning the MDX queries)  2) Internal Factors:- Is some slow MDX query / multiple mdx queries running at the same time, which was not running when you had tested it before? Is there any locking happening due to proactive caching or processing operations? Are the measure group caches being cleared by processing operations? (Ans : Again, profiler and perfmon counters will help in finding it out. Load testing can be done using AS Performance Workbench (http://asperfwb.codeplex.com/) by running multiple queries at once)  3) External factors:- Is some other application competing for the same resources?  HINT : Read “Identifying and Resolving MDX Query Performance Bottlenecks in SQL Server 2005 Analysis Services” (http://sqlcat.com/whitepapers/archive/2007/12/16/identifying-and-resolving-mdx-query-performance-bottlenecks-in-sql-server-2005-analysis-services.aspx) Well, these are great tips. Now win big prizes by participate in my question over 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

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• SQL SERVER – Validating Spatial Object with IsValidDetailed Function

  - by pinaldave

  What do you prefer – error or warning indicating error may happen with the reason for the error. While writing the previous statement I remember the movie “Minory Report”. This blog post is not about minority report but I will still cover the concept in a single statement “Let us predict the future and prevent the crime which is about to happen in future”. (Please feel free to correct me if I am wrong about the movie concept, I really do not want to hurt your sentiment if you are dedicated fan). Let us switch to the SQL Server world. Spatial data types are interesting concepts. I love writing about spatial data types because it allows me to be creative with shapes (just like toddlers). When working with Spatial Datatypes it is all good when the spatial object works fine. However, when the spatial object has issue or it is created with invalid coordinates it used to give a simple error that there is an issue with the object but did not provide much information. This made it very difficult to debug. If this spatial object was used in the big procedure and while this big procedural error out because of the invalid spatial object, it is indeed very difficult to debug it. I always wished that the more information provided regarding what is the problem with spatial datatype. SQL Server 2012 has introduced the new function IsValidDetailed(). This function has made my life very easy. In simple words this function will check if the spatial object passed is valid or not. If it is valid it will give information that it is valid. If the spatial object is not valid it will return the answer that it is not valid and the reason for the same. This makes it very easy to debug the issue and make the necessary correction. DECLARE @p GEOMETRY = 'Polygon((2 2, 6 6, 4 2, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'Polygon((2 2, 3 3, 4 4, 5 5, 6 6, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'Polygon((2 2, 4 4, 4 2, 2 3, 2 2))' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'CIRCULARSTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'CIRCULARSTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO DECLARE @p GEOMETRY = 'LINESTRING(2 2, 4 4, 0 0)' SELECT @p.IsValidDetailed() GO Here is the resultset of the above query. You can see any valid query and some invalid query. If the query is invalid it also demonstrates the reason along with the error message. 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: Spatial Database, SQL Spatial

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• SQLAuthority News – Presenting at Great Indian Developer Summit 2012 – SQL Server Misconception and Resolutions

  - by pinaldave

  Earlier during TechEd 2012, I presented a session on SQL Server Misconception and Resolutions. It was a pleasure to present this session with Vinod Kumar during the event. Great Indian Developer Summit is around the corner and I will be presenting there once again with the same topic. We had an excellent response during the last event; the hall was so filled, but there were plenty who were not able to get into the session as there was no place for them to sit or stand inside. Well, here is another chance for all who missed the presentation. New Additions During the last session, we were a two-presenter tag team, and we presented the session in a sense that it would suit two speakers in one stage. But this time, I am the only presenter, so I decided to present this session in a much different way. I will still assume there are two presenters. One of the presenters will be me, of course, and the second person will be YOU! Yes, you read that right – you will be presenting this session with me. If you wonder how, well, you will have to attend the session to figure it out. Talking Points We will be talking about the following topics in the session which we will relate to SQL Server: Moon Landing Napoléon Bonaparte Wall of China Bollywood …and of course, SQL Server itself. I promise that this 45 minute- presentation will be the one of the highlights of the event for you. Goodies I can only promise 20 goodies as of the moment. I might bring more when you meet me there. Session Details Title: SQL Server Misconceptions and Resolution – A Practical Perspective (Add to Calendar) Abstract: “The earth is flat”! – An ancient common misconception, which has been proven incorrect as we progressed in modern times. In this session, we will see various database misconceptions prevailing and their resolutions with the aid of the demos. In this unique session, the audience will be a part of the conversation and resolution. Date and Time: April 17, 2012, 16:55 to 17:40 Location: J. N. Tata Auditorium, National Science Symposium Complex (NSSC), Bangalore, India Add to Calendar Reference : Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, T SQL, Technology

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• SQL SERVER – How to easily work with Database Diagrams

  - by Pinal Dave

  Databases are very widely used in the modern world. Regardless of the complexity of a database, each one requires in depth designing. To practice along please Download dbForge Studio now.  The right methodology of designing a database is based on the foundations of data normalization, according to which we should first define database’s key elements – entities. Afterwards the attributes of entities and relations between them are determined. There is a strong opinion that the process of database designing should start with a pencil and a blank sheet of paper. This might look old-fashioned nowadays, because SQL Server provides a much wider functionality for designing databases – Database Diagrams. When using SSMS for working with Database Diagrams I realized two things – on the one hand, visualization of a scheme allows designing a database more efficiently; on the other – when it came to creating a big scheme, some difficulties occurred when designing with SSMS. The alternatives haven’t taken long to wait and dbForge Studio for SQL Server is one of them. Its functions offer more advantages for working with Database Diagrams. For example, unlike SSMS, dbForge Studio supports an opportunity to drag-and-drop several tables at once from the Database Explorer. This is my opinion but personally I find this option very useful. Another great thing is that a diagram can be saved as both a graphic file and a special XML file, which in case of identical environment can be easily opened on the other server for continuing the work. During working with dbForge Studio it turned out that it offers a wide set of elements to operate with on the diagram. Noteworthy among such elements are containers which allow aggregating diagram objects into thematic groups. Moreover, you can even place an image directly on the diagram if the scheme design is based on a standard template. Each of the development environments has a different approach to storing a diagram (for example, SSMS stores them on a server-side, whereas dbForge Studio – in a local file). I haven’t found yet an ability to convert existing diagrams from SSMS to dbForge Studio. However I hope Devart developers will implement this feature in one of the following releases. All in all, editing Database Diagrams through dbForge Studio was a nice experience and allowed speeding-up the common database designing tasks. Download dbForge Studio now. 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

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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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• SQL SERVER – Script to Update a Specific Column in Entire Database

  - by Pinal Dave

  Last week, I have received a very interesting question and I find in email and I really liked the question as I had to play around with SQL Script for a while to come up with the answer he was looking for. Please read the question and I believe that all of us face this kind of situation. “Pinal, In our database we have recently introduced ModifiedDate column in all of the tables. Now onwards any update happens in the row, we are updating current date and time to that field. Now here is the issue, when we added that field we did not update it with a default value because we were not sure when we will go live with the system so we let it be NULL. Now modification to the application went live yesterday and we are now updating this field. Here is where I need your help. We need to update all the tables in our database where we have column created ModifiedDate and now want to update with current datetime. As our system is already live since yesterday there are several thousands of the rows which are already updated with real world value so we do not want to update those values. Essentially, in our entire database where ever there is a ModifiedDate column and if it is NULL we want to update that with current date time?  Do you have a script for it?” Honestly I did not have such a script. This is very specific required but I was able to come up with two different methods how he can use this method. Method 1 : Using INFORMATION_SCHEMA SELECT 'UPDATE ' + T.TABLE_SCHEMA + '.' + T.TABLE_NAME + ' SET ModifiedDate = GETDATE() WHERE ModifiedDate IS NULL;' FROM INFORMATION_SCHEMA.TABLES T INNER JOIN INFORMATION_SCHEMA.COLUMNS C ON T.TABLE_NAME = C.TABLE_NAME AND c.COLUMN_NAME ='ModifiedDate' WHERE T.TABLE_TYPE = 'BASE TABLE' ORDER BY T.TABLE_SCHEMA, T.TABLE_NAME; Method 2: Using DMV SELECT 'UPDATE ' + SCHEMA_NAME(t.schema_id) + '.' + t.name + ' SET ModifiedDate = GETDATE() WHERE ModifiedDate IS NULL;' FROM sys.tables AS t INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID WHERE c.name ='ModifiedDate' ORDER BY SCHEMA_NAME(t.schema_id), t.name; Above scripts will create an UPDATE script which will do the task which is asked. We can pretty much the update script to any other SELECT statement and retrieve any other data as well. Click to Download Scripts 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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