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• SQL SERVER – Video – Performance Improvement in Columnstore Index

  - by pinaldave

  I earlier wrote an article about SQL SERVER – Fundamentals of Columnstore Index and it got very well accepted in community. However, one of the suggestion I keep on receiving for that article is that many of the reader wanted to see columnstore index in the action but they were not able to do that. Some of the readers did not install SQL Server 2012 or some did not have good machine to recreate the big table involved in the demo. For the same reason, I have created small video for that. I have written two more article on columstore index. Please read them as followup to the video: SQL SERVER – How to Ignore Columnstore Index Usage in Query SQL SERVER – Updating Data in A Columnstore Index Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video

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• SQL SERVER – Weekly Series – Memory Lane – #006

  - 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 This was my very first year of blogging so I was every day learning something new. As I have said many times, that blogging was never an intention. I had really not understood what exactly I am working on or beginning when I was beginning blogging in 2006. I had never knew that my life was going to change forever, once I started blogging. When I look back all of this year, I am happy that we are here together. 2007 IT Outsourcing to India – Top 10 Reasons Companies Outsource Outsourcing is about trust, collaboration and success. Helping other countries in need has been always the course of mankind, outsourcing is nothing different then that. With information technology and process improvements increasing the complexity, costs and skills required to accomplish routine tasks as well as challenging complex tasks, companies are outsourcing such tasks to providers who have the expertise to perform them at lower costs , with greater value and quality outcome. UDF – Remove Duplicate Chars From String This was a very interesting function I wrote in my early career. I am still using this function when I have to remove duplicate chars from strings. I have yet to come across a scenario where it does not work so I keep on using it till today. Please leave a comment if there is any better solution to this problem. FIX : Error : 3702 Cannot drop database because it is currently in use This is a very generic error when DROP Database is command is executed and the database is not dropped. The common mistake user is kept the connection open with this database and trying to drop the database. The database cannot be dropped if there is any other connection open along with it. It is always a good idea to take database in single user mode before dropping it. Here is the quick tutorial regarding how to bring the database in single user mode: Using T-SQL | Using SSMS. 2008 Install SQL Server 2008 – How to Upgrade to SQL Server 2008 – Installation Tutorial This was indeed one of the most popular articles in SQL Server 2008. Lots of people wanted to learn how to install SQL SErver 2008 but they were facing various issues while installation. I build this tutorial which becomes reference points for many. Default Collation of SQL Server 2008 What is the collation of SQL Server 2008 default installations? I often see this question confusing many experienced developers as well. Well the answer is in following image. Ahmedabad SQL Server User Group Meeting – November 2008 User group meetings are fun, now a days I am going to User Group meetings every week but there was a case when I have been just a beginner on this subject. The bug of the community was caught on me years ago when I started to present in Ahmedabad and Gandhinagar SQ LServer User Groups. 2009 Validate an XML document in TSQL using XSD My friend Jacob Sebastian wrote an excellent article on the subject XML and XSD. Because of the ‘eXtensible’ nature of XML (eXtensible Markup Language), often there is a requirement to restrict and validate the content of an XML document to a pre-defined structure and values. XSD (XML Schema Definition Language) is the W3C recommended language for describing and validating XML documents. SQL Server implements XSD as XML Schema Collections. Star Join Query Optimization At present, when queries are sent to very large databases, millions of rows are returned. Also the users have to go through extended query response times when joining multiple tables are involved with such queries. ‘Star Join Query Optimization’ is a new feature of SQL Server 2008 Enterprise Edition. This mechanism uses bitmap filtering for improving the performance of some types of queries by the effective retrieval of rows from fact tables. 2010 These puzzles are very interesting and intriguing – there was lots of interest on this subject. If you have free time this weekend. You may want to try them out. SQL SERVER – Challenge – Puzzle – Usage of FAST Hint (Solution)  SQL SERVER – Puzzle – Challenge – Error While Converting Money to Decimal (Solution)  SQL SERVER – Challenge – Puzzle – Why does RIGHT JOIN Exists (Open)  Additionally, I had great fun presenting SQL Server Performance Tuning seminar at fantastic locations in Hyderabad. Installing AdventeWorks Database This has been the most popular request I have received on my blog. Here is the quick video about how one can install AdventureWorks. 2011 Effect of SET NOCOUNT on @@ROWCOUNT There was an interesting incident once while I was presenting a session. I wrote a code and suddenly 10 hands went up in the air.  This was a bit surprise to me as I do not know why they all got alerted. I assumed that there should be something wrong with either project, screen or my display. However the real reason was very interesting – I suggest you read the complete blog post to understand this interesting scenario. Error: Deleting Offline Database and Creating the Same Name This is very interesting because once a user deletes the offline database the MDF and LDF file still exists and if the user attempts to create a new database with the same name it will give error. I found this very interesting and the blog explains the concept very quickly. Have you ever faced a similar 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 – 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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• Controlling ASP.NET output cache memory usage

  - by Josh Einstein

  I would like to use output caching with WCF Data Services and although there's nothing specifically built in to support caching, there is an OnStartProcessingRequest method that allows me to hook in and set the cacheability of the request using normal ASP.NET mechanisms. But I am worried about the worker process getting recycled due to excessive memory consumption if large responses are cached. Is there a way to specify an upper limit for the ASP.NET output cache so that if this limit is exceeded, items in the cache will be discarded? I've seen the caching configuration settings but I get the impression from the documentation that this is for explicit caching via the Cache object since there is a separate outputCacheSettings which has no memory-related attributes. Here's a code snippet from Scott Hanselman's post that shows how I'm setting the cacheability of the request. protected override void OnStartProcessingRequest(ProcessRequestArgs args) { base.OnStartProcessingRequest(args); //Cache for a minute based on querystring HttpContext context = HttpContext.Current; HttpCachePolicy c = HttpContext.Current.Response.Cache; c.SetCacheability(HttpCacheability.ServerAndPrivate); c.SetExpires(HttpContext.Current.Timestamp.AddSeconds(60)); c.VaryByHeaders["Accept"] = true; c.VaryByHeaders["Accept-Charset"] = true; c.VaryByHeaders["Accept-Encoding"] = true; c.VaryByParams["*"] = true; }

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• SQL SERVER – Weekly Series – Memory Lane – #037

  - by Pinal Dave

  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. 2007 Convert Text to Numbers (Integer) – CAST and CONVERT If table column is VARCHAR and has all the numeric values in it, it can be retrieved as Integer using CAST or CONVERT function. List All Stored Procedure Modified in Last N Days If SQL Server suddenly start behaving in un-expectable behavior and if stored procedure were changed recently, following script can be used to check recently modified stored procedure. If a stored procedure was created but never modified afterwards modified date and create a date for that stored procedure are same. Count Duplicate Records – Rows Validate Field For DATE datatype using function ISDATE() We always checked DATETIME field for incorrect data type. One of the user input date as 30/2/2007. The date was sucessfully inserted in the temp table but while inserting from temp table to final table it crashed with error. We had now task to validate incorrect date value before we insert in final table. Jr. Developer asked me how can he do that? We check for incorrect data type (varchar, int, NULL) but this is incorrect date value. Regular expression works fine with them because of mm/dd/yyyy format. 2008 Find Space Used For Any Particular Table It is very simple to find out the space used by any table in the database. Two Convenient Features Inline Assignment – Inline Operations Here is the script which does both – Inline Assignment and Inline Operation DECLARE @idx INT = 0 SET @idx+=1 SELECT @idx Introduction to SPARSE Columns SPARSE column are better at managing NULL and ZERO values in SQL Server. It does not take any space in database at all. If column is created with SPARSE clause with it and it contains ZERO or NULL it will be take lesser space then regular column (without SPARSE clause). SP_CONFIGURE – Displays or Changes Global Configuration Settings If advanced settings are not enabled at configuration level SQL Server will not let user change the advanced features on server. Authorized user can turn on or turn off advance settings. 2009 Standby Servers and Types of Standby Servers Standby Server is a type of server that can be brought online in a situation when Primary Server goes offline and application needs continuous (high) availability of the server. There is always a need to set up a mechanism where data and objects from primary server are moved to secondary (standby) server. BLOB – Pointer to Image, Image in Database, FILESTREAM Storage When it comes to storing images in database there are two common methods. I had previously blogged about the same subject on my visit to Toronto. With SQL Server 2008, we have a new method of FILESTREAM storage. However, the answer on when to use FILESTREAM and when to use other methods is still vague in community. 2010 Upper Case Shortcut SQL Server Management Studio I select the word and hit CTRL+SHIFT+U and it SSMS immediately changes the case of the selected word. Similar way if one want to convert cases to lower case, another short cut CTRL+SHIFT+L is also available. The Self Join – Inner Join and Outer Join Self Join has always been a noteworthy case. It is interesting to ask questions about self join in a room full of developers. I often ask – if there are three kinds of joins, i.e.- Inner Join, Outer Join and Cross Join; what type of join is Self Join? The usual answer is that it is an Inner Join. However, the reality is very different. Parallelism – Row per Processor – Row per Thread – Thread 0  If you look carefully in the Properties window or XML Plan, there is “Thread 0?. What does this “Thread 0” indicate? Well find out from the blog post. How do I Learn and How do I Teach The blog post has raised three very interesting questions. How do you learn? How do you teach? What are you learning or teaching? Let me try to answer the same. 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 7 of 31 What are Different Types of Locks? What are Pessimistic Lock and Optimistic Lock? When is the use of UPDATE_STATISTICS command? What is the Difference between a HAVING clause and a WHERE clause? What is Connection Pooling and why it is Used? What are the Properties and Different Types of Sub-Queries? What are the Authentication Modes in SQL Server? How can it be Changed? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 8 of 31 Which Command using Query Analyzer will give you the Version of SQL Server and Operating System? What is an SQL Server Agent? Can a Stored Procedure call itself or a Recursive Stored Procedure? How many levels of SP nesting is possible? What is Log Shipping? Name 3 ways to get an Accurate Count of the Number of Records in a Table? What does it mean to have QUOTED_IDENTIFIER ON? What are the Implications of having it OFF? What is the Difference between a Local and a Global Temporary Table? What is the STUFF Function and How Does it Differ from the REPLACE Function? What is PRIMARY KEY? What is UNIQUE KEY Constraint? What is FOREIGN KEY? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 9 of 31 What is CHECK Constraint? What is NOT NULL Constraint? What is the difference between UNION and UNION ALL? What is B-Tree? How to get @@ERROR and @@ROWCOUNT at the Same Time? What is a Scheduled Job or What is a Scheduled Task? What are the Advantages of Using Stored Procedures? What is a Table Called, if it has neither Cluster nor Non-cluster Index? What is it Used for? Can SQL Servers Linked to other Servers like Oracle? What is BCP? When is it Used? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 10 of 31 What Command do we Use to Rename a db, a Table and a Column? What are sp_configure Commands and SET Commands? How to Implement One-to-One, One-to-Many and Many-to-Many Relationships while Designing Tables? What is Difference between Commit and Rollback when Used in Transactions? What is an Execution Plan? When would you Use it? How would you View the Execution Plan? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 11 of 31 What is Difference between Table Aliases and Column Aliases? Do they Affect Performance? What is the difference between CHAR and VARCHAR Datatypes? What is the Difference between VARCHAR and VARCHAR(MAX) Datatypes? What is the Difference between VARCHAR and NVARCHAR datatypes? Which are the Important Points to Note when Multilanguage Data is Stored in a Table? How to Optimize Stored Procedure Optimization? What is SQL Injection? How to Protect Against SQL Injection Attack? How to Find Out the List Schema Name and Table Name for the Database? What is CHECKPOINT Process in the SQL Server? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 12 of 31 How does Using a Separate Hard Drive for Several Database Objects Improves Performance Right Away? How to Find the List of Fixed Hard Drive and Free Space on Server? Why can there be only one Clustered Index and not more than one? What is Difference between Line Feed (\n) and Carriage Return (\r)? Is It Possible to have Clustered Index on Separate Drive From Original Table Location? What is a Hint? How to Delete Duplicate Rows? Why the Trigger Fires Multiple Times in Single Login? 2012 CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis Shortcut key is CTRL+SHIFT+]. This key can be very useful when dealing with multiple subqueries, CTE or query with multiple parentheses. When exercised this shortcut key it selects T-SQL code between two parentheses. Monday Morning Puzzle – Query Returns Results Sometimes but Not Always I am beginner with SQL Server. I have one query, it sometime returns a result and sometime it does not return me the result. Where should I start looking for a solution and what kind of information I should send to you so you can help me with solving. I have no clue, please guide me. Remove Debug Button in SSMS – SQL in Sixty Seconds #020 – Video Effect of Case Sensitive Collation on Resultset Collation is a very interesting concept but I quite often see it is heavily neglected. I have seen developer and DBA looking for a workaround to fix collation error rather than understanding if the side effect of the workaround. Switch Between Two Parenthesis using Shortcut CTRL+] Earlier this week I wrote a blog post about CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis, I received quite a lot of positive feedback from readers. If you are a regular reader of the blog post, you must be aware that I appreciate the learning shared by readers. 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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• How do I break down MySQL query results into categories, each with a specific number of rows?

  - by Mel

  Hello, Problem: I want to list n number of games from each genre (order not important) The following MySQL query resides inside a ColdFusion function. It is meant to list all games under a platform (for example, list all PS3 games; list all Xbox 360 games; etc...). The variable for PlatformID is passed through the URL. I have 9 genres, and I would like to list 10 games from each genre. SELECT games.GameID AS GameID, games.GameReleaseDate AS rDate, titles.TitleName AS tName, titles.TitleShortDescription AS sDesc, genres.GenreName AS gName, platforms.PlatformID, platforms.PlatformName AS pName, platforms.PlatformAbbreviation AS pAbbr FROM (((games join titles on((games.TitleID = titles.TitleID))) join genres on((genres.GenreID = games.GenreID))) join platforms on((platforms.PlatformID = games.PlatformID))) WHERE (games.PlatformID = '#ARGUMENTS.PlatformID#') ORDER BY GenreName ASC, GameReleaseDate DESC Once the query results come back I group them in ColdFusion as follows: <cfoutput query="ListGames" group="gName"> (first loop which lists genres) #ListGames.gName# <cfoutput> (nested loop which lists games) #ListGames.tName# </cfoutput> </cfoutput> The problem is that I only want 10 games from each genre to be listed. If I place a "limit" of 50 in the SQL, I will get ~ 50 games of the same genre (depending on how much games of that genre there are). The second issue is I don't want the overload of querying the database for all games when each person will only look at a few. What is the correct way to do this? Many thanks!

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• Does query plan optimizer works well with joined/filtered table-valued functions?

  - by smoothdeveloper

  In SQLSERVER 2005, I'm using table-valued function as a convenient way to perform arbitrary aggregation on subset data from large table (passing date range or such parameters). I'm using theses inside larger queries as joined computations and I'm wondering if the query plan optimizer work well with them in every condition or if I'm better to unnest such computation in my larger queries. Does query plan optimizer unnest table-valued functions if it make sense? If it doesn't, what do you recommend to avoid code duplication that would occur by manually unnesting them? If it does, how do you identify that from the execution plan? code sample: create table dbo.customers ( [key] uniqueidentifier , constraint pk_dbo_customers primary key ([key]) ) go /* assume large amount of data */ create table dbo.point_of_sales ( [key] uniqueidentifier , customer_key uniqueidentifier , constraint pk_dbo_point_of_sales primary key ([key]) ) go create table dbo.product_ranges ( [key] uniqueidentifier , constraint pk_dbo_product_ranges primary key ([key]) ) go create table dbo.products ( [key] uniqueidentifier , product_range_key uniqueidentifier , release_date datetime , constraint pk_dbo_products primary key ([key]) , constraint fk_dbo_products_product_range_key foreign key (product_range_key) references dbo.product_ranges ([key]) ) go . /* assume large amount of data */ create table dbo.sales_history ( [key] uniqueidentifier , product_key uniqueidentifier , point_of_sale_key uniqueidentifier , accounting_date datetime , amount money , quantity int , constraint pk_dbo_sales_history primary key ([key]) , constraint fk_dbo_sales_history_product_key foreign key (product_key) references dbo.products ([key]) , constraint fk_dbo_sales_history_point_of_sale_key foreign key (point_of_sale_key) references dbo.point_of_sales ([key]) ) go create function dbo.f_sales_history_..snip.._date_range ( @accountingdatelowerbound datetime, @accountingdateupperbound datetime ) returns table as return ( select pos.customer_key , sh.product_key , sum(sh.amount) amount , sum(sh.quantity) quantity from dbo.point_of_sales pos inner join dbo.sales_history sh on sh.point_of_sale_key = pos.[key] where sh.accounting_date between @accountingdatelowerbound and @accountingdateupperbound group by pos.customer_key , sh.product_key ) go -- TODO: insert some data -- this is a table containing a selection of product ranges declare @selectedproductranges table([key] uniqueidentifier) -- this is a table containing a selection of customers declare @selectedcustomers table([key] uniqueidentifier) declare @low datetime , @up datetime -- TODO: set top query parameters . select saleshistory.customer_key , saleshistory.product_key , saleshistory.amount , saleshistory.quantity from dbo.products p inner join @selectedproductranges productrangeselection on p.product_range_key = productrangeselection.[key] inner join @selectedcustomers customerselection on 1 = 1 inner join dbo.f_sales_history_..snip.._date_range(@low, @up) saleshistory on saleshistory.product_key = p.[key] and saleshistory.customer_key = customerselection.[key] I hope the sample makes sense. Much thanks for your help!

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• SQL SERVER – Template Browser – A Very Important and Useful Feature of SSMS

  - by pinaldave

  Let me start today’s blog post with a direction question. How many of you have ever used Template Browser? Template Browser is a very important and useful feature of SQL Server Management Studio (SSMS). Every time when I am talking about SQL Server there is always someone comes up with the question, why there is no step by step procedure included in SSMS for features. Honestly every time I get this question, the question I ask back is How many of you have ever used Template Browser? I think the answer to this question is most of the time either no or we have not heard of the feature. One of the people asked me back – have you ever written about it on your blog? I have not yet written about it. Basically there is nothing much to write about it. It is pretty straight forward feature, like any other feature and it is indeed difficult to elaborate. However, I will try to give a quick introduction to this feature. Templates are like a quick cheat sheet or quick reference. Templates are available to create objects like databases, tables, views, indexes, stored procedures, triggers, statistics, and functions. Templates are also available for Analysis Services as well. The template scripts contain parameters to help you customize the code. You can Replace Template Parameters dialog box to insert values into the script. Additionally users can create new custom templates as well with folder structure. To open a template from Template Explorer Go to View menu >> Template Explorer or type CTRL+ALT+L. You will find a list of categories click on any category and expand the folder structure. For our sample example let us expand Index Folder. In this folder you will notice the various T-SQL Scripts. These scripts can be opened by double click or can be dragged to editor area and modified as needed. Sample template is now available in the query editor area with all the necessary parameter place folder. You can replace the same parameter by typing either CTRL+SHIFT+M or by going to Query Menu >> Specify Values for Template Parameters. In this screen it will show  Specify Values for Template Parameters dialog box, accept the value or replace it with a new value. This will now get your script ready to go. Check it one more time and change the script to fit your requirement. I personally use template explorer for two things. First one is obviously for templates but the hidden one and an important one is for learning new features and T-SQL commands. There is so much to learn and so little time. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Detect Virtual Log Files (VLF) in LDF

  - by pinaldave

  In one of the recent training engagements, I was asked if it true that there are multiple small log files in the large log file (LDF). I found this question very interesting as the answer is yes. Multiple small Virtual Log Files commonly known as VLFs together make an LDF file. The writing of the VLF is sequential and resulting in the writing of the LDF file is sequential as well. This leads to another talk that one does not need more than one log file in most cases. However, in short, you can use following DBCC command to know how many Virtual Log Files or VLFs are present in your log file. DBCC LOGINFO You can find the result of above query to something as displayed in following image. You can see the column which is marked as 2 which means it is active VLF and the one with 0 which is inactive VLF. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Big Data – Buzz Words: What is NewSQL – Day 10 of 21

  - by Pinal Dave

  In yesterday’s blog post we learned the importance of the relational database. In this article we will take a quick look at the what is NewSQL. What is NewSQL? NewSQL stands for new scalable and high performance SQL Database vendors. The products sold by NewSQL vendors are horizontally scalable. NewSQL is not kind of databases but it is about vendors who supports emerging data products with relational database properties (like ACID, Transaction etc.) along with high performance. Products from NewSQL vendors usually follow in memory data for speedy access as well are available immediate scalability. NewSQL term was coined by 451 groups analyst Matthew Aslett in this particular blog post. On the definition of NewSQL, Aslett writes: “NewSQL” is our shorthand for the various new scalable/high performance SQL database vendors. We have previously referred to these products as ‘ScalableSQL‘ to differentiate them from the incumbent relational database products. Since this implies horizontal scalability, which is not necessarily a feature of all the products, we adopted the term ‘NewSQL’ in the new report. And to clarify, like NoSQL, NewSQL is not to be taken too literally: the new thing about the NewSQL vendors is the vendor, not the SQL. In other words - NewSQL incorporates the concepts and principles of Structured Query Language (SQL) and NoSQL languages. It combines reliability of SQL with the speed and performance of NoSQL. Categories of NewSQL There are three major categories of the NewSQL New Architecture – In this framework each node owns a subset of the data and queries are split into smaller query to sent to nodes to process the data. E.g. NuoDB, Clustrix, VoltDB MySQL Engines – Highly Optimized storage engine for SQL with the interface of MySQ Lare the example of such category. E.g. InnoDB, Akiban Transparent Sharding – This system automatically split database across multiple nodes. E.g. Scalearc  Summary In simple words – NewSQL is kind of database following relational database principals and provides scalability like NoSQL. Tomorrow In tomorrow’s blog post we will discuss about the Role of Cloud Computing in Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Squid handling of concurrent cache misses

  - by Oliver H-H

  We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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• HTML5 Web Storage Cleared when Browser Clear Cache?

  - by jiewmeng

  i wonder if HTML5 Web Storage will be cleared when browser clears its cache? if it did, many ppl like me may lose data if i accidentally clear cache? or like in this comment ... Since HTML5 local storage is kept separate from js cookies (like Silverlight, Gears, Flash), it opens up a world of 3rd party privacy issues for HTML5 as these objects will likely NOT get deleted with a clear cache or delete temporary data ... where web storage is not cleared, but leads to privacy issues?

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• Castle Active Record - Working with the cache

  - by David

  Hi All, im new to the Castle Active Record Pattern and Im trying to get my head around how to effectivley use cache. So what im trying to do (or want to do) is when calling the GetAll, find out if I have called it before and check the cache, else load it, but I also want to pass a bool paramter that will force the cache to clear and requery the db. So Im just looking for the final bits. thanks public static List<Model.Resource> GetAll(bool forceReload) { List<Model.Resource> resources = new List<Model.Resource>(); //Request to force reload if (forceReload) { //need to specify to force a reload (how?) XmlConfigurationSource source = new XmlConfigurationSource("appconfig.xml"); ActiveRecordStarter.Initialize(source, typeof(Model.Resource)); resources = Model.Resource.FindAll().ToList(); } else { //Check the cache somehow and return the cache? } return resources; } public static List<Model.Resource> GetAll() { return GetAll(false); }

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• SQL SERVER – Retrieving Random Rows from Table Using NEWID()

  - by pinaldave

  I have previously written about how to get random rows from SQL Server. SQL SERVER – Generate A Single Random Number for Range of Rows of Any Table – Very interesting Question from Reader SQL SERVER – Random Number Generator Script – SQL Query However, I have not blogged about following trick before. Let me share the trick here as well. You can generate random scripts using following methods as well. USE AdventureWorks2012 GO -- Method 1 SELECT TOP 100 * FROM Sales.SalesOrderDetail ORDER BY NEWID() GO -- Method 2 SELECT TOP 100 * FROM Sales.SalesOrderDetail ORDER BY CHECKSUM(NEWID()) GO You will notice that using NEWID() in the ORDER BY will return random rows in the result set. How many of you knew this trick? You can run above script multiple times and it will give random rows every single time. 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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• UserControl: How to set Output Cache duration programaticaly?

  - by ParagM

  UserControl: How to set Output Cache duration programaticaly?

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• Mysql: ROLLBACK for multiple queries

  - by Raj

  Hi I have more than three MySql queiries in a PHP script triggered by scheduled task. If a query catch an error, script throw an exception and rollback that Mysql query. It works fine. However if first query works fine, but not 2nd query, throw an exception, it rollback 2nd one but not 1st query. I am using begin_trans(), commit and rollback() for individual queries because Sometimes i need to rollback one query, sometimes all queries. Is there any way to rollback one query or all queries? Thanks in advance UPDATE: I got it working, there was no problem with in begin_trans(), commit and rollback(), the database connection config was different for one query from other queries, crazy code without any comments!!!

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• write behind cache Ehcache new feature?

  - by cometta

  Hi, i looking for guide/document/tutorial on how to use this new feature write-behind-cache in ehcache? Is there any demo in spring+jpa+ehcache+hibernate? just to clariyfing, write-behind-cache mean each time we persist entity, it will be written into cache rather than into database correct?

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• Struts 2 discard cache header

  - by Dewfy

  I have strange discarding behavior of struts2 while setting cache option for my image. I'm trying to put image from db to be cached on client side To render image I use ( http://struts.apache.org/2.x/docs/how-can-we-display-dynamic-or-static-images-that-can-be-provided-as-an-array-of-bytes.html ) where special result type render as follow: public void execute(ActionInvocation invocation) throws Exception { ...//some preparation HttpServletResponse response = ServletActionContext.getResponse(); HttpServletRequest request = ServletActionContext.getRequest(); ServletOutputStream os = response.getOutputStream(); try { byte[] imageBytes = action.getImage(); response.setContentType("image/gif"); response.setContentLength(imageBytes.length); //I want cache up to 10 min Date future = new Date(((new Date()).getTime() + 1000 * 10*60l)); ; response.addDateHeader("Expires", future.getTime()); response.setHeader("Cache-Control", "max-age=" + 10*60 + ""); response.addHeader("cache-Control", "public"); response.setHeader("ETag", request.getRequestURI()); os.write(imageBytes); } catch(Exception e) { response.sendError(HttpServletResponse.SC_NOT_FOUND); } os.flush(); os.close(); } But when image is embedded to page it is always reloaded (Firebug shows code 200), and neither Expires, nor max-age are presented in header Host localhost:9090 Accept image/png,image/*;q=0.8,*/*;q=0.5 Accept-Language en-us,en;q=0.5 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 300 Connection keep-alive Referer http://localhost:9090/web/result?matchId=1 Cookie JSESSIONID=4156BEED69CAB0B84D950932AB9EA1AC; If-None-Match /web/_srv/teamcolor Cache-Control max-age=0 I have no idea why it is dissapered, may be problem in url? It is forms with parameter: http://localhost:9090/web/_srv/teamcolor?loginId=3

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• Help with MySQL query... Need help ordering a group of rows

  - by user156814

  I can tell it best by explaining the query I have, and what I need. I need to be able to get a group of items from the database, grouped by category, manufacturer, and year made. The groupings need to be sorted based on total amount of items within the group. This part is done with the query below. Secondly, I need to be able to show an image of the most expensive item out of the group, which is why I use MAX(items.current_price). I thought MAX() gets the ENTIRE row corresponding to the largest column value. I was wrong, as MAX only gets the numeric value of the largest price. So the query doesnt work well for that. SELECT items.id, items.year, items.manufacturer, COUNT(items.id) AS total, MAX(items.current_price) AS price, items.gallery_url, FROM ebay AS items WHERE items.primary_category_id = 213 AND items.year <> '' AND items.manufacturer <> '' AND items.bad_item <> 1 GROUP BY items.primary_category_id, items.manufacturer, items.year ORDER BY total DESC, price ASC LIMIT 10 if that doesnt explain it well, the results should be something like this id 10548 year 1989 manufacturer bowman total 451 price 8500.00 (The price of the most expensive item in the table/ not the price of item 10548) gallery_url http://ebay.xxxxx (The image of item 10548) A little help please. Thanks

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• Queue access to the database to avoid multiple cache items

  - by MikeJ

  I have a music related ASP.NET web site which caches a lot of static information from the database on the first request. Sometimes, the application is reset and cache is cleared while the application is on heavy load and then all http requests go to the database to retrieve that static data and cache it for other requests. How can I ensure that only one request go to the database and cache the results, so that other request simply read that info from cache and not needlessly retrieve the same info over and over again. Can I use thread locking? For example, can I do something like lock(this) { db access here }?

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• how to diffrentiate between same field names of two tables in a select query??

  - by developer

  i have more than two tables in my database and all of them contains same field names like table A table B table C field1 field1 field1 field2 field2 field2 field3 field3 field3 . . . . . . . . . . . . I have to write a SELECT query which gets almost all same fields from these 3 tables.Iam using something like this :- select a.field1,a.field2,a.field3,b.field1,b.field2,b.field3,c.field1,c.field2,c.field3 from table A as a, table B as b,table C as c where so and so. but when i print field1's value it gives me the last table values. How can i get all the values of three tables with the same field names??? do i have to write individual query for every table OR there is any ways of fetching them all in a single query????

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• Why would using a Temp table be faster than a nested query?

  - by Mongus Pong

  We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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• Firefox not honoring must-revalidate cache headers returned by jQuery.ajax() request

  - by Oliver Weichhold

  UPDATE 1: Judging by this thread I am not the only one having this problem in FF 12 and only in 12. UPDATE 2: The problem does not seem to be limited to Ajax requests. From the looks of it everything that makes it into Firefox 12's cache will be fetched from there. No matter what. The server can specify cache control headers all day long. Bummer! What I'm trying to achieve is the following behavior: Browser may cache the response without revalidating for up to 5 minutes I don't care if the browser revalidates on every request (Both Chrome and IE9 do for example) When the expiration is up the browser MUST revalidate (which in my case will result in fresh data) Chrome and IE9 exhibit the desired behavior when issuing a jquery.ajax() request with ifModified: true and cache: true while Firefox 12 never revalidates, which poses a serious problem. These are the actual response headers: HTTP/1.1 200 OK Server: nginx Date: Sun, 03 Jun 2012 07:13:43 GMT Content-Type: text/javascript; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive Vary: Accept-Encoding Cache-Control: private, must-revalidate, max-age=300 Last-Modified: Sun, 03 Jun 2012 07:07:13 GMT Content-Encoding: gzip Any suggestions?

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• How to remove/hide <div></div> tags only without the content?

  - by candies

  For example I have: <div id ="test">[the content here]</div> The content within the div tags will appear after I called the id of div using ajax. This is the code: function dinamic(add) { var kode = add.value; if (!kode) return; xmlhttp2.open('get', '../template/get_id.php?kode='+kode, true); xmlhttp2.onreadystatechange = function() { if ((xmlhttp2.readyState == 4) && (xmlhttp2.status == 200)) { var add = document.getElementById("test"); add.innerHTML = xmlhttp2.responseText; } return false; } xmlhttp2.send(null); } So it will appear <div id="test">A</div> I'd like to put the content of div - A into mysql query. $test = $_GET['test']; $query = "select * from example where category='$test'"; I've tried to make variable $test of the div id to get the content but result of the query in category is none. I tried again, I put the div in to the query $query = "select * from example where category='<div id=\"test\">A</div>'"; Yes, It works. But when I did query on navicat, no results I got because there's spaces between A that is <div> and </div>. How to remove/hide the div tags only so its only appear the content? > $query = "select * from example where category='A'"; < Edit: If I echo the query on firefox browser will say "$query = "select * from example where category='[space]A[space]'";" And look at the bug(I use firebug), it will say "$query = "select * from example where category='<div id="test">A</div>'";" So my guessing why can't get result after query on navicat is there's spaces between A([space]A[space]), just have no idea how to remove/hide the div tags, I want to get this result only "$query = "select * from example where category='A'";" Thanks.

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• How can I clear the Android app cache?

  - by Srao

  I am writing a app which can programatically clear application cache of all the third party apps installed on the device. Following is the code snippet for Android 2.2 public static void trimCache(Context myAppctx) { Context context = myAppctx.createPackageContext("com.thirdparty.game", Context.CONTEXT_INCLUDE_CO|Context.CONTEXT_IGNORE_SECURITY); File cachDir = context.getCacheDir(); Log.v("Trim", "dir " + cachDir.getPath()); if (cachDir!= null && cachDir.isDirectory()) { Log.v("Trim", "can read " + cachDir.canRead()); String[] fileNames = cachDir.list(); //Iterate for the fileName and delete } } My manifest has following permissions: android.permission.CLEAR_APP_CACHE android.permission.DELETE_CACHE_FILES Now the problem is that the name of the cache directory is printed but the list of files cachDir.list() always returns null. I am not able to delete the cache directory since the file list is always null. Is there any other way to clear the application cache?

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