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• SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*)

  - by pinaldave

  Earlier I have published Puzzle Why SELECT * throws an error but SELECT COUNT(*) does not. This question have received many interesting comments. Let us go over few of the answers, which are valid. Before I start the same, let me acknowledge Rob Farley who has not only answered correctly very first but also started interesting conversation in the same thread. The usual question will be what is the right answer. I would like to point to official Microsoft Connect Items which discusses the same. RGarvao https://connect.microsoft.com/SQLServer/feedback/details/671475/select-test-where-exists-select tiberiu utan http://connect.microsoft.com/SQLServer/feedback/details/338532/count-returns-a-value-1 Rob Farley count(*) is about counting rows, not a particular column. It doesn’t even look to see what columns are available, it’ll just count the rows, which in the case of a missing FROM clause, is 1. “select *” is designed to return columns, and therefore barfs if there are none available. Even more odd is this one: select ‘blah’ where exists (select *) You might be surprised at the results… Koushik The engine performs a “Constant scan” for Count(*) where as in the case of “SELECT *” the engine is trying to perform either Index/Cluster/Table scans. amikolaj When you query ‘select * from sometable’, SQL replaces * with the current schema of that table. With out a source for the schema, SQL throws an error. so when you query ‘select count(*)’, you are counting the one row. * is just a constant to SQL here. Check out the execution plan. Like the description states – ‘Scan an internal table of constants.’ You could do ‘select COUNT(‘my name is adam and this is my answer’)’ and get the same answer. Netra Acharya SELECT * Here, * represents all columns from a table. So it always looks for a table (As we know, there should be FROM clause before specifying table name). So, it throws an error whenever this condition is not satisfied. SELECT COUNT(*) Here, COUNT is a Function. So it is not mandetory to provide a table. Check it out this: DECLARE @cnt INT SET @cnt = COUNT(*) SELECT @cnt SET @cnt = COUNT(‘x’) SELECT @cnt Naveen Select 1 / Select ‘*’ will return 1/* as expected. Select Count(1)/Count(*) will return the count of result set of select statement. Count(1)/Count(*) will have one 1/* for each row in the result set of select statement. Select 1 or Select ‘*’ result set will contain only 1 result. so count is 1. Where as “Select *” is a sysntax which expects the table or equauivalent to table (table functions, etc..). It is like compilation error for that query. Ramesh Hi Friends, Count is an aggregate function and it expects the rows (list of records) for a specified single column or whole rows for *. So, when we use ‘select *’ it definitely give and error because ‘*’ is meant to have all the fields but there is not any table and without table it can only raise an error. So, in the case of ‘Select Count(*)’, there will be an error as a record in the count function so you will get the result as ’1'. Try using : Select COUNT(‘RAMESH’) and think there is an error ‘Must specify table to select from.’ in place of ‘RAMESH’ Pinal : If i am wrong then please clarify this. Sachin Nandanwar Any aggregate function expects a constant or a column name as an expression. DO NOT be confused with * in an aggregate function.The aggregate function does not treat it as a column name or a set of column names but a constant value, as * is a key word in SQL. You can replace any value instead of * for the COUNT function.Ex Select COUNT(5) will result as 1. The error resulting from select * is obvious it expects an object where it can extract the result set. I sincerely thank you all for wonderful conversation, I personally enjoyed it and I am sure all of you have the same feeling. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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• How to get full query string parameters not UrlDecoded

  - by developerit

  Introduction While developing Developer IT’s website, we came across a problem when the user search keywords containing special character like the plus ‘+’ char. We found it while looking for C++ in our search engine. The request parameter output in ASP.NET was “c “. I found it strange that it removed the ‘++’ and replaced it with a space… Analysis After a bit of Googling and Reflection, it turns out that ASP.NET calls UrlDecode on each parameters retreived by the Request(“item”) method. The Request.Params property is affected by this two since it mashes all QueryString, Forms and other collections into a single one. Workaround Finally, I solve the puzzle usign the Request.RawUrl property and parsing it with the same RegEx I use in my url re-writter. The RawUrl not affected by anything. As its name say it, it’s raw. Published on http://www.developerit.com/

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• SQL SERVER – Puzzle – SELECT * vs SELECT COUNT(*)

  - by pinaldave

  Earlier this weekend I have presented at Bangalore User Group on the subject of SQL Server Tips and Tricks. During the presentation I have asked a question to attendees. It was very interesting to see that I have received various different answer to my question. Here is the same question for you and I would like to see what your answer to this question. Question: SELECT * gives error when executed alone but SELECT COUNT(*) does not. Why? Select * - resulting Error Select count * - NOT resulting Error Please leave your answer as comment over here. If you prefer you can blog post about this on your blog and put a link here. I will publish valid answer with due credit in future blog posts. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• HTML muliple select should look like HTML select

  - by GustlyWind

  Hi I am trying to use a HTML select box with 'multiple' select options and size to 1 as below ` <SELECT NAME="toppings" MULTIPLE SIZE=5> <OPTION VALUE="mushrooms">mushrooms <OPTION VALUE="greenpeppers">green peppers </SELECT> When the size is set to 1 small scrollbar appears which makes the page clumsy.If I increase the size its eating up my page since there are around 20 such multiple boxes in and around the page. I am looking for a solution which looks like <SELECT> but should function as multiple Is this possible. I remember seen something similar but don't remember exactly. Any ideas

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• MySQL Query Select using sub-select takes too long

  - by True Soft

  I noticed something strange while executing a select from 2 tables: SELECT * FROM table_1 WHERE id IN ( SELECT id_element FROM table_2 WHERE column_2=3103); This query took approximatively 242 seconds. But when I executed the subquery SELECT id_element FROM table_2 WHERE column_2=3103 it took less than 0.002s (and resulted 2 rows). Then, when I did SELECT * FROM table_1 WHERE id IN (/* prev.result */) it was the same: 0.002s. I was wondering why MySQL is doing the first query like that, taking much more time than the last 2 queries separately? Is it an optimal solution for selecting something based from the results of a sub-query? Other details: table_1 has approx. 9000 rows, and table_2 has 90000 rows. After I added an index on column_2 from table_2, the first query took 0.15s.

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• How to select non-consecutive options of multiple select using keyboard in IE

  - by Yan

  Using only keyboard, how can I select non-consecutive options of a multiple select element. On Firefox or Windows explorer, I can simply ctrl+Arrow to move the focus and then space bar to select. But I don't see any way to make it work on IE. Thanks

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• SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table)

  - by pinaldave

  Few days ago I wrote article about SQL SERVER – Stored Procedure Optimization Tips – Best Practices. I received lots of comments on particular blog article. In fact, almost all the comments are very interesting. If you have not read all the comments, I strongly suggest to read them. Click here to read the comments. The [...]

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

  - by pinaldave

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

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• SQL select statement from 2 tables

  - by Steven

  Hi, I have a small sql question. I have 2 tables Members and Managers Members has: memberID, Name, Address Managers has: memberID, EditRights, DeleteRights EditRights and DeleteRights are of type bit. Mangers have a relationship with Members, because they are members themselves. I want to select all members id's, name and adress and for the members that are managers show if they have editrights and/or deleterights. SO: Exmaple data Members: ID, Name, Address 1, tom, 2 flat 2, dan, 3 flat 3, ben, 4 flat 4, bob, 6 flat 5, sam, 9 flat Managers: ID, Editrights, deleterights 2, 0, 1 4, 1, 1 5, 0, 0 I would like to display a select like this: 1, tom, 2 flat, no rights 2, dan, 3 flat, Delete 3, ben, 4 flat, no rights 4, bob, 6 flat, Edit&Delete 5, sam, 9 flat, no rights Any help would be great

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• SQL University: Parallelism Week - Part 2, Query Processing

  - by Adam Machanic

  Welcome back for the second part of Parallelism Week here at SQL University . Get your pencils ready, and make sure to raise your hand if you have a question. Last time we covered the necessary background material to help you understand how the SQL Server Operating System schedules its many active threads, and the differences between its behavior and that of the Windows operating system's scheduler. We also discussed some of the variations on the theme of parallel processing. Today we'll take a look...(read more)

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• Complex query making site extremely slow

  - by Basit

  select SQL_CALC_FOUND_ROWS DISTINCT media.*, username from album as album, album_permission as permission, user as user, media as media , word_tag as word_tag, tag as tag where ((media.album_id = album.album_id and album.private = 'yes' and album.album_id = permission.album_id and (permission.email = '' or permission.user_id = '') ) or (media.album_id = album.album_id and album.private = 'no' ) or media.album_id = '0' ) and media.status = '1' and media.user_id = user.user_id and word_tag.media_id = media.media_id and word_tag.tag_id = tag.tag_id and tag.name in ('justin','bieber','malfunction','katherine','heigl','wardrobe','cinetube') and media.media_type = 'video' and media.media_id not in ('YHL6a5z8MV4') group by media.media_id order by RAND() #there is limit too, by 20 rows.. i dont know where to begin explaining about this query, but please forgive me and ask me if you have any question. following is the explanation. SQL_CALC_FOUND_ROWS is calculating how many rows are there and will be using for pagination, so it counts total records, even tho only 20 is showing. DISTINCT will stop the repeated row to display. username is from user table. album, album_permission. its checking if album is private and if it is, then check if user has permission, by user_id. i think rest is easy to understand, but if you need to know more about it, then please ask. im really frustrated by this query and site is very slow or not opening sometimes cause of this query. please help

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• Changing options in select box based on different select options

  - by yogsma

  I have 2 select options. I want to change the drop down options in second select options based on what I select in first select options. How do I do that in jquery? <select id="Manage"> <option value="a">A</option> <option value="b">B</option> <option value="c">C</option> <select> Second select option if A is selected from first select option <select id='selectA'> <option value="1">1</option> <option value="2">2</option> </select> Now if B is selected from first select option <select id='selectA'> <option value="3">3</option> <option value="4">4</option> </select>

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• SQL SERVER – SSMS Automatically Generates TOP (100) PERCENT in Query Designer

  - by pinaldave

  Earlier this week, I was surfing various SQL forums to see what kind of help developer need in the SQL Server world. One of the question indeed caught my attention. I am here regenerating complete question as well scenario to illustrate the point in a precise manner. Additionally, I have added added second part of the question to give completeness. Question: I am trying to create a view in Query Designer (not in the New Query Window). Every time I am trying to create a view it always adds  TOP (100) PERCENT automatically on the T-SQL script. No matter what I do, it always automatically adds the TOP (100) PERCENT to the script. I have attempted to copy paste from notepad, build a query and a few other things – there is no success. I am really not sure what I am doing wrong with Query Designer. Here is my query script: (I use AdventureWorks as a sample database) SELECT Person.Address.AddressID FROM Person.Address INNER JOIN Person.AddressType ON Person.Address.AddressID = Person.AddressType.AddressTypeID ORDER BY Person.Address.AddressID This script automatically replaces by following query: SELECT TOP (100) PERCENT Person.Address.AddressID FROM Person.Address INNER JOIN Person.AddressType ON Person.Address.AddressID = Person.AddressType.AddressTypeID ORDER BY Person.Address.AddressID However, when I try to do the same from New Query Window it works totally fine. However, when I attempt to create a view of the same query it gives following error. Msg 1033, Level 15, State 1, Procedure myView, Line 6 The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified. It is pretty clear to me now that the script which I have written seems to need TOP (100) PERCENT, so Query . Why do I need it? Is there any work around to this issue. I particularly find this question pretty interesting as it really touches the fundamentals of the T-SQL query writing. Please note that the query which is automatically changed is not in New Query Editor but opened from SSMS using following way. Database >> Views >> Right Click >> New View (see the image below) Answer: The answer to the above question can be very long but I will keep it simple and to the point. There are three things to discuss in above script 1) Reason for Error 2) Reason for Auto generates TOP (100) PERCENT and 3) Potential solutions to the above error. Let us quickly see them in detail. 1) Reason for Error The reason for error is already given in the error. ORDER BY is invalid in the views and a few other objects. One has to use TOP or other keywords along with it. The way semantics of the query works where optimizer only follows(honors) the ORDER BY in the same scope or the same SELECT/UPDATE/DELETE statement. There is a possibility that one can order after the scope of the view again the efforts spend to order view will be wasted. The final resultset of the query always follows the final ORDER BY or outer query’s order and due to the same reason optimizer follows the final order of the query and not of the views (as view will be used in another query for further processing e.g. in SELECT statement). Due to same reason ORDER BY is now allowed in the view. For further accuracy and clear guidance I suggest you read this blog post by Query Optimizer Team. They have explained it very clear manner the same subject. 2) Reason for Auto Generated TOP (100) PERCENT One of the most popular workaround to above error is to use TOP (100) PERCENT in the view. Now TOP (100) PERCENT allows user to use ORDER BY in the query and allows user to overcome above error which we discussed. This gives the impression to the user that they have resolved the error and successfully able to use ORDER BY in the View. Well, this is incorrect as well. The way this works is when TOP (100) PERCENT is used the result is not guaranteed as well it is ignored in our the query where the view is used. Here is the blog post on this subject: Interesting Observation – TOP 100 PERCENT and ORDER BY. Now when you create a new view in the SSMS and build a query with ORDER BY to avoid the error automatically it adds the TOP 100 PERCENT. Here is the connect item for the same issue. I am sure there will be more connect items as well but I could not find them. 3) Potential Solutions If you are reading this post from the beginning in that case, it is clear by now that ORDER BY should not be used in the View as it does not serve any purpose unless there is a specific need of it. If you are going to use TOP 100 PERCENT with ORDER BY there is absolutely no need of using ORDER BY rather avoid using it all together. Here is another blog post of mine which describes the same subject ORDER BY Does Not Work – Limitation of the Views Part 1. It is valid to use ORDER BY in a view if there is a clear business need of using TOP with any other percentage lower than 100 (for example TOP 10 PERCENT or TOP 50 PERCENT etc). In most of the cases ORDER BY is not needed in the view and it should be used in the most outer query for present result in desired order. User can remove TOP 100 PERCENT and ORDER BY from the view before using the view in any query or procedure. In the most outer query there should be ORDER BY as per the business need. I think this sums up the concept in a few words. This is a very long topic and not easy to illustrate in one single blog post. I welcome your comments and suggestions. 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, SQL View, T SQL, Technology

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• How to optimize this MySQL query

  - by James Simpson

  This query was working fine when the database was small, but now that there are millions of rows in the database, I am realizing I should have looked at optimizing this earlier. It is looking at over 600,000 rows and is Using where; Using temporary; Using filesort (which leads to an execution time of 5-10 seconds). It is using an index on the field 'battle_type.' SELECT username, SUM( outcome ) AS wins, COUNT( * ) - SUM( outcome ) AS losses FROM tblBattleHistory WHERE battle_type = '0' && outcome < '2' GROUP BY username ORDER BY wins DESC , losses ASC , username ASC LIMIT 0 , 50

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• Nesting Linq-to-Objects query within Linq-to-Entities query –what is happening under the covers?

  - by carewithl

  var numbers = new int[] { 1, 2, 3, 4, 5 }; var contacts = from c in context.Contacts where c.ContactID == numbers.Max() | c.ContactID == numbers.FirstOrDefault() select c; foreach (var item in contacts) Console.WriteLine(item.ContactID); Linq-to-Entities query is first translated into Linq expression tree, which is then converted by Object Services into command tree. And if Linq-to-Entities query nests Linq-to-Objects query, then this nested query also gets translated into an expression tree. a) I assume none of the operators of the nested Linq-to-Objects query actually get executed, but instead data provider for particular DB (or perhaps Object Services) knows how to transform the logic of Linq-to-Objects operators into appropriate SQL statements? b) Data provider knows how to create equivalent SQL statements only for some of the Linq-to-Objects operators? c) Similarly, data provider knows how to create equivalent SQL statements only for some of the non-Linq methods in the Net Framework class library? EDIT: I know only some Sql so I can't be completely sure, but reading Sql query generated for the above code it seems data provider didn't actually execute numbers.Max method, but instead just somehow figured out that numbers.Max should return the maximum value and then proceed to include in generated Sql query a call to TSQL's build-in MAX function. It also put all the values held by numbers array into a Sql query. SELECT CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN '0X0X' ELSE '0X1X' END AS [C1], [Extent1].[ContactID] AS [ContactID], [Extent1].[FirstName] AS [FirstName], [Extent1].[LastName] AS [LastName], [Extent1].[Title] AS [Title], [Extent1].[AddDate] AS [AddDate], [Extent1].[ModifiedDate] AS [ModifiedDate], [Extent1].[RowVersion] AS [RowVersion], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[CustomerTypeID] END AS [C2], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[InitialDate] END AS [C3], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[PrimaryDesintation] END AS [C4], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[SecondaryDestination] END AS [C5], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[PrimaryActivity] END AS [C6], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[SecondaryActivity] END AS [C7], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[Notes] END AS [C8], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[RowVersion] END AS [C9], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[BirthDate] END AS [C10], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[HeightInches] END AS [C11], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[WeightPounds] END AS [C12], CASE WHEN (([Project1].[C1] = 1) AND ([Project1].[C1] IS NOT NULL)) THEN [Project1].[DietaryRestrictions] END AS [C13] FROM [dbo].[Contact] AS [Extent1] LEFT OUTER JOIN (SELECT [Extent2].[ContactID] AS [ContactID], [Extent2].[BirthDate] AS [BirthDate], [Extent2].[HeightInches] AS [HeightInches], [Extent2].[WeightPounds] AS [WeightPounds], [Extent2].[DietaryRestrictions] AS [DietaryRestrictions], [Extent3].[CustomerTypeID] AS [CustomerTypeID], [Extent3].[InitialDate] AS [InitialDate], [Extent3].[PrimaryDesintation] AS [PrimaryDesintation], [Extent3].[SecondaryDestination] AS [SecondaryDestination], [Extent3].[PrimaryActivity] AS [PrimaryActivity], [Extent3].[SecondaryActivity] AS [SecondaryActivity], [Extent3].[Notes] AS [Notes], [Extent3].[RowVersion] AS [RowVersion], cast(1 as bit) AS [C1] FROM [dbo].[ContactPersonalInfo] AS [Extent2] INNER JOIN [dbo].[Customers] AS [Extent3] ON [Extent2].[ContactID] = [Extent3].[ContactID]) AS [Project1] ON [Extent1].[ContactID] = [Project1].[ContactID] LEFT OUTER JOIN (SELECT TOP (1) [c].[C1] AS [C1] FROM (SELECT [UnionAll3].[C1] AS [C1] FROM (SELECT [UnionAll2].[C1] AS [C1] FROM (SELECT [UnionAll1].[C1] AS [C1] FROM (SELECT 1 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable1] UNION ALL SELECT 2 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable2]) AS [UnionAll1] UNION ALL SELECT 3 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable3]) AS [UnionAll2] UNION ALL SELECT 4 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable4]) AS [UnionAll3] UNION ALL SELECT 5 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable5]) AS [c]) AS [Limit1] ON 1 = 1 LEFT OUTER JOIN (SELECT TOP (1) [c].[C1] AS [C1] FROM (SELECT [UnionAll7].[C1] AS [C1] FROM (SELECT [UnionAll6].[C1] AS [C1] FROM (SELECT [UnionAll5].[C1] AS [C1] FROM (SELECT 1 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable6] UNION ALL SELECT 2 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable7]) AS [UnionAll5] UNION ALL SELECT 3 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable8]) AS [UnionAll6] UNION ALL SELECT 4 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable9]) AS [UnionAll7] UNION ALL SELECT 5 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable10]) AS [c]) AS [Limit2] ON 1 = 1 CROSS JOIN (SELECT MAX([UnionAll12].[C1]) AS [A1] FROM (SELECT [UnionAll11].[C1] AS [C1] FROM (SELECT [UnionAll10].[C1] AS [C1] FROM (SELECT [UnionAll9].[C1] AS [C1] FROM (SELECT 1 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable11] UNION ALL SELECT 2 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable12]) AS [UnionAll9] UNION ALL SELECT 3 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable13]) AS [UnionAll10] UNION ALL SELECT 4 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable14]) AS [UnionAll11] UNION ALL SELECT 5 AS [C1] FROM (SELECT 1 AS X) AS [SingleRowTable15]) AS [UnionAll12]) AS [GroupBy1] WHERE [Extent1].[ContactID] IN ([GroupBy1].[A1], (CASE WHEN ([Limit1].[C1] IS NULL) THEN 0 ELSE [Limit2].[C1] END)) Based on this, is it possible that Linq2Entities provider indeed doesn't execute non-Linq and Linq-to-Object methods, but instead creates equivalent SQL statements for some of them ( and for others it throws an exception )? Thank you in advance

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• SQL SERVER – Tricks to Replace SELECT * with Column Names – SQL in Sixty Seconds #017 – Video

  - by pinaldave

  You might have heard many times that one should not use SELECT * as there are many disadvantages to the usage of the SELECT *. I also believe that there are always rare occasion when we need every single column of the query. In most of the cases, we only need a few columns of the query and we should retrieve only those columns. SELECT * has many disadvantages. Let me list a few and remaining you can add as a comment.  Retrieves unnecessary columns and increases network traffic When a new columns are added views needs to be refreshed manually Leads to usage of sub-optimal execution plan Uses clustered index in most of the cases instead of using optimal index It is difficult to debug. There are two quick tricks I have discussed in the video which explains how users can avoid using SELECT * but instead list the column names. 1) Drag the columns folder from SQL Server Management Studio to Query Editor 2) Right Click on Table Name >> Script TAble AS >> SELECT To… >> Select option It is extremely easy to list the column names in the table. In today’s sixty seconds video, you will notice that I was able to demonstrate both the methods very quickly. From now onwards there should be no excuse for not listing ColumnName. Let me ask a question back – is there ever a reason to SELECT *? If yes, would you please share that as a comment. More on SELECT *: SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*) SQL SERVER – Puzzle – SELECT * vs SELECT COUNT(*) SQL SERVER – SELECT vs. SET Performance Comparison I encourage you to submit your ideas for SQL in Sixty Seconds. We will try to accommodate as many as we can. If we like your idea we promise to share with you educational material. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video

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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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• SQL SERVER – Select and Delete Duplicate Records – SQL in Sixty Seconds #036 – Video

  - by pinaldave

  Developers often face situations when they find their column have duplicate records and they want to delete it. A good developer will never delete any data without observing it and making sure that what is being deleted is the absolutely fine to delete. Before deleting duplicate data, one should select it and see if the data is really duplicate. In this video we are demonstrating two scripts – 1) selects duplicate records 2) deletes duplicate records. We are assuming that the table has a unique incremental id. Additionally, we are assuming that in the case of the duplicate records we would like to keep the latest record. If there is really a business need to keep unique records, one should consider to create a unique index on the column. Unique index will prevent users entering duplicate data into the table from the beginning. This should be the best solution. However, deleting duplicate data is also a very valid request. If user realizes that they need to keep only unique records in the column and if they are willing to create unique constraint, the very first requirement of creating a unique constraint is to delete the duplicate records. Let us see how to connect the values in Sixty Seconds: Here is the script which is used in the video. USE tempdb GO CREATE TABLE TestTable (ID INT, NameCol VARCHAR(100)) GO INSERT INTO TestTable (ID, NameCol) SELECT 1, 'First' UNION ALL SELECT 2, 'Second' UNION ALL SELECT 3, 'Second' UNION ALL SELECT 4, 'Second' UNION ALL SELECT 5, 'Second' UNION ALL SELECT 6, 'Third' GO -- Selecting Data SELECT * FROM TestTable GO -- Detecting Duplicate SELECT NameCol, COUNT(*) TotalCount FROM TestTable GROUP BY NameCol HAVING COUNT(*) > 1 ORDER BY COUNT(*) DESC GO -- Deleting Duplicate DELETE FROM TestTable WHERE ID NOT IN ( SELECT MAX(ID) FROM TestTable GROUP BY NameCol) GO -- Selecting Data SELECT * FROM TestTable GO DROP TABLE TestTable GO Related Tips in SQL in Sixty Seconds: SQL SERVER – Delete Duplicate Records – Rows SQL SERVER – Count Duplicate Records – Rows SQL SERVER – 2005 – 2008 – Delete Duplicate Rows Delete Duplicate Records – Rows – Readers Contribution Unique Nonclustered Index Creation with IGNORE_DUP_KEY = ON – A Transactional Behavior What would you like to see in the next SQL in Sixty Seconds video? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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• triying to do a combo select with this.val() but it doesnt show the second select

  - by irenkai

  Im triying to do a combo where the when the user selects Chile out of the select box, a second select shows up showing the cities. The jQuery code Im using is this. $(document).ready(function(){var ciudad = $("#ciudad"); ciudad.css("display","none"); $("select#selectionpais").change(function(){ var hearValue = $("select#selectionpais").val(); if( hearValue == "chile"){ ciudad.css("display","block"); ; }else{ ciudad.css("display","none") } }); }); and the Html is this (abreviated for the sake of understanding) <select name="pais" id="selectionpais"> .... Chile Afganistán and the second select (the one that should be shown is this) <select id="ciudad" name="ciudad" class="ciudad"> Santiago Anyone has a clue why it isnt working?

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• SQL SERVER – Grouping by Multiple Columns to Single Column as A String

  - by pinaldave

  One of the most common questions I receive in email is how to group multiple column data in comma separate values in a single row grouping by another column. I have previously blogged about it in following two blog posts. However, both aren’t addressing the following exact problem. Comma Separated Values (CSV) from Table Column Comma Separated Values (CSV) from Table Column – Part 2 The question comes in many different formats but in following image I am demonstrating the same question in simple words. This is the most popular question on my Facebook page as well. (Example) Here is the sample script to build the sample dataset. CREATE TABLE TestTable (ID INT, Col VARCHAR(4)) GO INSERT INTO TestTable (ID, Col) SELECT 1, 'A' UNION ALL SELECT 1, 'B' UNION ALL SELECT 1, 'C' UNION ALL SELECT 2, 'A' UNION ALL SELECT 2, 'B' UNION ALL SELECT 2, 'C' UNION ALL SELECT 2, 'D' UNION ALL SELECT 2, 'E' GO SELECT * FROM TestTable GO Here is the solution which will build an answer to the above question. -- Get CSV values SELECT t.ID, STUFF( (SELECT ',' + s.Col FROM TestTable s WHERE s.ID = t.ID FOR XML PATH('')),1,1,'') AS CSV FROM TestTable AS t GROUP BY t.ID GO I hope this is an easy solution. I am going to point to this blog post in the future for all the similar questions. Final Clean Up Act -- Clean up DROP TABLE TestTable GO Here is the question back to you - Is there any better way to write above script? Please leave a comment and I will write a separate blog post with due credit. 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: SQL XML

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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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• How to Export Multiple Contacts in Outlook 2013 to Multiple vCards or a Single vCard

  - by Lori Kaufman

  We’ve shown you how to export a contact to and import a contact from a vCard (.vcf) file. However, what if you want to export multiple contacts at the same time to multiple vCard files or even a single vCard file? Outlook doesn’t allow you to directly export all your contacts as vCard files or as a single vCard file, but there is a way to accomplish both tasks. Export Multiple Contacts to Multiple vCard Files Outlook allows you to forward contact information as a vCard. You can also select multiple contacts and forward them all at once. This feature allows you to indirectly export multiple contacts at once to multiple vCard files. Click the People tab to access your contacts. Select all the contacts you want to export using the Shift and Ctrl keys as needed. Select Contacts the same way you would select files in Windows Explorer. Click Forward Contact in the Share section on the Home tab and select As a Business Card from the drop-down menu. The selected contacts attached to a new email message as .vcf files. To select all the attached .vcf files, right-click in the Attached box and select Select All from the popup menu. Make sure the folder to which you want to export the contacts is open in Windows Explorer. Drag the selected attached .vcf files from the new email message to the open folder in Windows Explorer. A .vcf file is created for each contact you selected and dragged to the folder. You can close the Message window by clicking on the X in the upper, right corner of the window. NOTE: You can also close the Message window by clicking the File tab. Then, click the Close option on the left. Because you already have your .vcf files, you don’t need to save or send the message, so click No when asked if you want to save your changes. If it turns out that a draft of your message was saved, the following message displays. Click No to delete the draft. Export Multiple Contacts to a Single vCard (.vcf) File If you would rather export your contacts to a single vCard (.vcf) File, there is a way to do this using Gmail. We’ll export the contacts from Outlook as a .csv file and then use Gmail to convert the .csv file to a .vcf file. Select the contacts you want to export on the People page and click the File tab. On the Account Information screen, click Open & Export in the list on the left. On the Open screen, click Import/Export. The Import and Export Wizard displays. Select Export to a file from the Choose an action to perform list and click Next. In the Create a file of type box, select Comma Separated Values. Click Next. Contacts should be already selected in the Select folder to export from box. If not, select it. Click Next. Click Browse to the right of the Save exported file as box. Navigate to the folder to which you want to export the .csv file. Enter a name for the file in the File name edit box, keeping the .csv extension. The path you selected is entered into the Save exported file as edit box. Click Next. The final screen of the Export to a File dialog box displays listing the action to be performed. Click Finish to begin the export process. Once the export process is finished, you will see the .csv file in the folder in Windows Explorer. Now, we will import the .csv file into Gmail. Go to Gmail and sign in to your account. Click Gmal in the upper, left corner of the main page and select Contacts from the drop-down menu. On the Contacts page, click More above your list of contacts and select Import from the drop-down menu. Click Browse on the Import contacts dialog box that displays. Navigate to the folder in which you saved the .csv file and select the file. Click Open. Click Import on the Import contacts dialog box. A screen displays listing the contacts you imported, but not yet merged into your main Gmail contacts list. Select the contacts you imported. NOTE: The contacts you imported may be the only contacts in this list. If that’s the case, they all should be automatically selected. Click More and select Export from the drop-down menu. On the Export contacts dialog box, select Selected contacts to indicate which contacts you want to export. NOTE: We could have selected The group Imported 10/10/13 because that contains the same two contacts as the Selected contacts. Select vCard format for the export format. Click Export. Gmail creates a contacts.vcf file containing the selected contacts and asks you whether you want to open the file with Outlook or save the file. To save the file, select the Save File option and click OK. Navigate to the folder in which you want to save the contacts.vcf file, change the name of the file in the File name edit box, if desired, and click Save. The .vcf file is saved to the selected directory and contains all the contacts you exported from Outlook. This could be used as a way to backup your contacts in one file. You could also backup the .csv file. However, if you have a lot of contacts you will probably find that the .vcf file is smaller. We only exported two contacts, and our .csv file was 2 KB, while the .vcf file was 1 KB. We will be showing you how to import multiple contacts from a single .vcf file into Outlook soon.     

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• "select * from table" vs "select colA,colB,etc from table" interesting behaviour in SqlServer2005

  - by kristof

  Apology for a lengthy post but I needed to post some code to illustrate the problem. Inspired by the question What is the reason not to use select * ? posted a few minutes ago, I decided to point out some observations of the select * behaviour that I noticed some time ago. So let's the code speak for itself: IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[starTest]') AND type in (N'U')) DROP TABLE [dbo].[starTest] CREATE TABLE [dbo].[starTest]( [id] [int] IDENTITY(1,1) NOT NULL, [A] [varchar](50) NULL, [B] [varchar](50) NULL, [C] [varchar](50) NULL ) ON [PRIMARY] GO insert into dbo.starTest(a,b,c) select 'a1','b1','c1' union all select 'a2','b2','c2' union all select 'a3','b3','c3' go IF EXISTS (SELECT * FROM sys.views WHERE object_id = OBJECT_ID(N'[dbo].[vStartest]')) DROP VIEW [dbo].[vStartest] go create view dbo.vStartest as select * from dbo.starTest go go IF EXISTS (SELECT * FROM sys.views WHERE object_id = OBJECT_ID(N'[dbo].[vExplicittest]')) DROP VIEW [dbo].[vExplicittest] go create view dbo.[vExplicittest] as select a,b,c from dbo.starTest go select a,b,c from dbo.vStartest select a,b,c from dbo.vExplicitTest IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[starTest]') AND type in (N'U')) DROP TABLE [dbo].[starTest] CREATE TABLE [dbo].[starTest]( [id] [int] IDENTITY(1,1) NOT NULL, [A] [varchar](50) NULL, [B] [varchar](50) NULL, [D] [varchar](50) NULL, [C] [varchar](50) NULL ) ON [PRIMARY] GO insert into dbo.starTest(a,b,d,c) select 'a1','b1','d1','c1' union all select 'a2','b2','d2','c2' union all select 'a3','b3','d3','c3' select a,b,c from dbo.vExplicittest select a,b,c from dbo.vStartest If you execute the following query and look at the results of last 2 select statements, the results that you will see will be as follows: select a,b,c from dbo.vExplicittest a1 b1 c1 a2 b2 c2 a3 b3 c3 select a,b,c from dbo.vStartest a1 b1 d1 a2 b2 d2 a3 b3 d3 As you can see in the results of select a,b,c from dbo.vStartest the data of column c has been replaced with the data from colum d. I believe that is related to the way the views are compiled, my understanding is that the columns are mapped by column indexes (1,2,3,4) as apposed to names. I though I would post it as a warning for people using select * in their sql and experiencing unexpected behaviour. Note: If you rebuild the view that uses select * each time after you modify the table it will work as expected

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• multiple mysql_real_query() in while loop

  - by Steve

  It seems that when I have one mysql_real_query() function in a continuous while loop, the query will get executed OK. However, if multiple mysql_real_query() are inside the while loop, one right after the other. Depending on the query, sometimes neither the first query nor second query will execute properly. This seems like a threading issue to me. I'm wondering if the mysql c api has a way of dealing with this? Does anyone know how to deal with this? mysql_free_result() doesn't work since I am not even storing the results. //keep polling as long as stop character '-' is not read while(szRxChar != '-') { // Check if a read is outstanding if (HasOverlappedIoCompleted(&ovRead)) { // Issue a serial port read if (!ReadFile(hSerial,&szRxChar,1, &dwBytesRead,&ovRead)) { DWORD dwErr = GetLastError(); if (dwErr!=ERROR_IO_PENDING) return dwErr; } } // Wait 5 seconds for serial input if (!(HasOverlappedIoCompleted(&ovRead))) { WaitForSingleObject(hReadEvent,RESET_TIME); } // Check if serial input has arrived if (GetOverlappedResult(hSerial,&ovRead, &dwBytesRead,FALSE)) { // Wait for the write GetOverlappedResult(hSerial,&ovWrite, &dwBytesWritten,TRUE); //load tagBuffer with byte stream tagBuffer[i] = szRxChar; i++; tagBuffer[i] = 0; //char arrays are \0 terminated //run query with tagBuffer if( strlen(tagBuffer)==PACKET_LENGTH ) { sprintf(query,"insert into scan (rfidnum) values ('"); strcat(query, tagBuffer); strcat(query, "')"); mysql_real_query(&mysql,query,(unsigned int)strlen(query)); i=0; } mysql_real_query(&mysql,"insert into scan (rfidnum) values ('2nd query')",(unsigned int)strlen("insert into scan (rfid) values ('2nd query')")); mysql_free_result(res); } }

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• SQL SERVER – Discard Results After Query Execution – SSMS

  - by pinaldave

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

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