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

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

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  • Joins in LINQ to SQL

    - by rajbk
    The following post shows how to write different types of joins in LINQ to SQL. I am using the Northwind database and LINQ to SQL for these examples. NorthwindDataContext dataContext = new NorthwindDataContext(); Inner Join var q1 = from c in dataContext.Customers join o in dataContext.Orders on c.CustomerID equals o.CustomerID select new { c.CustomerID, c.ContactName, o.OrderID, o.OrderDate }; SELECT [t0].[CustomerID], [t0].[ContactName], [t1].[OrderID], [t1].[OrderDate]FROM [dbo].[Customers] AS [t0]INNER JOIN [dbo].[Orders] AS [t1] ON [t0].[CustomerID] = [t1].[CustomerID] Left Join var q2 = from c in dataContext.Customers join o in dataContext.Orders on c.CustomerID equals o.CustomerID into g from a in g.DefaultIfEmpty() select new { c.CustomerID, c.ContactName, a.OrderID, a.OrderDate }; SELECT [t0].[CustomerID], [t0].[ContactName], [t1].[OrderID] AS [OrderID], [t1].[OrderDate] AS [OrderDate]FROM [dbo].[Customers] AS [t0]LEFT OUTER JOIN [dbo].[Orders] AS [t1] ON [t0].[CustomerID] = [t1].[CustomerID] Inner Join on multiple //We mark our anonymous type properties as a and b otherwise//we get the compiler error "Type inferencce failed in the call to 'Join’var q3 = from c in dataContext.Customers join o in dataContext.Orders on new { a = c.CustomerID, b = c.Country } equals new { a = o.CustomerID, b = "USA" } select new { c.CustomerID, c.ContactName, o.OrderID, o.OrderDate }; SELECT [t0].[CustomerID], [t0].[ContactName], [t1].[OrderID], [t1].[OrderDate]FROM [dbo].[Customers] AS [t0]INNER JOIN [dbo].[Orders] AS [t1] ON ([t0].[CustomerID] = [t1].[CustomerID]) AND ([t0].[Country] = @p0) Inner Join on multiple with ‘OR’ clause var q4 = from c in dataContext.Customers from o in dataContext.Orders.Where(a => a.CustomerID == c.CustomerID || c.Country == "USA") select new { c.CustomerID, c.ContactName, o.OrderID, o.OrderDate }; SELECT [t0].[CustomerID], [t0].[ContactName], [t1].[OrderID], [t1].[OrderDate]FROM [dbo].[Customers] AS [t0], [dbo].[Orders] AS [t1]WHERE ([t1].[CustomerID] = [t0].[CustomerID]) OR ([t0].[Country] = @p0) Left Join on multiple with ‘OR’ clause var q5 = from c in dataContext.Customers from o in dataContext.Orders.Where(a => a.CustomerID == c.CustomerID || c.Country == "USA").DefaultIfEmpty() select new { c.CustomerID, c.ContactName, o.OrderID, o.OrderDate }; SELECT [t0].[CustomerID], [t0].[ContactName], [t1].[OrderID] AS [OrderID], [t1].[OrderDate] AS [OrderDate]FROM [dbo].[Customers] AS [t0]LEFT OUTER JOIN [dbo].[Orders] AS [t1] ON ([t1].[CustomerID] = [t0].[CustomerID]) OR ([t0].[Country] = @p0)

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  • How do I use wine's new multi-channel audio support?

    - by Forest
    Wine supposedly added Multi-channel support to the ALSA driver in a recent release. However, I haven't found any documentation about it or any reports of anyone successfully using it. I have 5.1 surround sound through ALSA (not Pulse) on my linux system, yet games in wine don't seem to use anything more than stereo, no matter which ALSA device I select in winecfg. Can someone explain what must be done to get wine games to use all my speakers for positional audio, or failing that, point me toward some useful documentation on the new multi-channel support?

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  • I have written an SQL query but I want to optimize it [closed]

    - by ankit gupta
    is there any way to do this using minimum no of joins and select? 2 tables are involved in this operation transaction_pci_details and transaction SELECT t6.transaction_pci_details_id, t6.terminal_id, t6.transaction_no, t6.transaction_id, t6.transaction_type, t6.reversal_flag, t6.transmission_date_time, t6.retrivel_ref_no, t6.card_no,t6.card_type, t6.expires_on, t6.transaction_amount, t6.currency_code, t6.response_code, t6.action_code, t6.message_reason_code, t6.merchant_id, t6.auth_code, t6.actual_trans_amnt, t6.bal_card_amnt, t5.sales_person_id FROM TRANSACTION AS t5 INNER JOIN ( SELECT t4.transaction_pci_details_id, t4.terminal_id, t4.transaction_no, t4.transaction_id, t4.transaction_type, t4.reversal_flag, t4.transmission_date_time, t4.retrivel_ref_no, t4.card_no, t4.card_type, t4.expires_on, t4.transaction_amount, t4.currency_code, t4.response_code, t4.action_code, t3.message_reason_code, t4.merchant_id, t4.auth_code, t4.actual_trans_amnt, t4.bal_card_amnt FROM ( SELECT* FROM transaction_pci_details WHERE message_reason_code LIKE '%OUT%'|| message_reason_code LIKE '%FAILED%' /*we can add date here*/ UNION ALL SELECT t2.transaction_pci_details_id, t2.terminal_id, t2.transaction_no, t2.transaction_id, t2.transaction_type, t2.reversal_flag, t2.transmission_date_time, t2.retrivel_ref_no, t2.card_no, t2.card_type, t2.expires_on, t2.transaction_amount, t2.currency_code, t2.response_code, t2.action_code, t2.message_reason_code, t2.merchant_id, t2.auth_code, t2.actual_trans_amnt, t2.bal_card_amnt FROM ( SELECT transaction_id FROM TRANSACTION WHERE transaction_type_id = 8 ) AS t1 INNER JOIN ( SELECT * FROM transaction_pci_details WHERE message_reason_code LIKE '%appro%' /*we can add date here*/ ) AS t2 ON t1.transaction_id = t2.transaction_id ) AS t3 INNER JOIN ( SELECT* FROM transaction_pci_details WHERE action_code LIKE '%REQ%' /*we can add date here*/ ) AS t4 ON t3.transaction_pci_details_id - t4.transaction_pci_details_id = 1 ) AS t6 ON t5.transaction_id = t6.transaction_id

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  • How to archive data from a table to a local or remote database in SQL 2005 and SQL 2008

    - by simonsabin
    Often you have the need to archive data from a table. This leads to a number of challenges 1. How can you do it without impacting users 2. How can I make it transactionally consistent, i.e. the data I put in the archive is the data I remove from the main table 3. How can I get it to perform well Points 1 is very much tied to point 3. If it doesn't perform well then the delete of data is going to cause lots of locks and thus potentially blocking. For points 1 and 3 refer to my previous posts DELETE-TOP-x-rows-avoiding-a-table-scan and UPDATE-and-DELETE-TOP-and-ORDER-BY---Part2. In essence you need to be removing small chunks of data from your table and you want to do that avoiding a table scan. So that deals with the delete approach but archiving is about inserting that data somewhere else. Well in SQL 2008 they introduced a new feature INSERT over DML (Data Manipulation Language, i.e. SQL statements that change data), or composable DML. The ability to nest DML statements within themselves, so you can past the results of an insert to an update to a merge. I've mentioned this before here SQL-Server-2008---MERGE-and-optimistic-concurrency. This feature is currently limited to being able to consume the results of a DML statement in an INSERT statement. There are many restrictions which you can find here http://msdn.microsoft.com/en-us/library/ms177564.aspx look for the section "Inserting Data Returned From an OUTPUT Clause Into a Table" Even with the restrictions what we can do is consume the OUTPUT from a DELETE and INSERT the results into a table in another database. Note that in BOL it refers to not being able to use a remote table, remote means a table on another SQL instance. To show this working use this SQL to setup two databases foo and fooArchive create database foo go --create the source table fred in database foo select * into foo..fred from sys.objects go create database fooArchive go if object_id('fredarchive',DB_ID('fooArchive')) is null begin     select getdate() ArchiveDate,* into fooArchive..FredArchive from sys.objects where 1=2       end go And then we can use this simple statement to archive the data insert into fooArchive..FredArchive select getdate(),d.* from (delete top (1)         from foo..Fred         output deleted.*) d         go In this statement the delete can be any delete statement you wish so if you are deleting by ids or a range of values then you can do that. Refer to the DELETE-TOP-x-rows-avoiding-a-table-scan post to ensure that your delete is going to perform. The last thing you want to do is to perform 100 deletes each with 5000 records for each of those deletes to do a table scan. For a solution that works for SQL2005 or if you want to archive to a different server then you can use linked servers or SSIS. This example shows how to do it with linked servers. [ONARC-LAP03] is the source server. begin transaction insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*') d commit transaction and to prove the transactions work try, you should get the same number of records before and after. select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive   begin transaction insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*') d rollback transaction   select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive The transactions are very important with this solution. Look what happens when you don't have transactions and an error occurs   select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive   insert into fooArchive..FredArchive select getdate(),d.* from openquery ([ONARC-LAP03],'delete top (1)                     from foo..Fred                     output deleted.*                     raiserror (''Oh doo doo'',15,15)') d                     select (select count(1) from foo..Fred) fred        ,(select COUNT(1) from fooArchive..FredArchive ) fredarchive Before running this think what the result would be. I got it wrong. What seems to happen is that the remote query is executed as a transaction, the error causes that to rollback. However the results have already been sent to the client and so get inserted into the

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  • SQL SERVER – Answer – Value of Identity Column after TRUNCATE command

    - by pinaldave
    Earlier I had one conversation with reader where I almost got a headache. I suggest all of you to read it before continuing this blog post SQL SERVER – Reseting Identity Values for All Tables. I believed that he faced this situation because he did not understand the difference between SQL SERVER – DELETE, TRUNCATE and RESEED Identity. I wrote a follow up blog post explaining the difference between them. I asked a small question in the second blog post and I received many interesting comments. Let us go over the question and its answer here one more time. Here is the scenario to set up the puzzle. Create Table with Seed Identity = 11 Insert Value and Check Seed (it will be 11) Reseed it to 1 Insert Value and Check Seed (it will be 2) TRUNCATE Table Insert Value and Check Seed (it will be 11) Let us see the T-SQL Script for the same. USE [TempDB] GO -- Create Table CREATE TABLE [dbo].[TestTable]( [ID] [int] IDENTITY(11,1) NOT NULL, [var] [nchar](10) NULL ) ON [PRIMARY] GO -- Build sample data INSERT INTO [TestTable] VALUES ('val') GO -- Select Data SELECT * FROM [TestTable] GO -- Reseed to 1 DBCC CHECKIDENT ('TestTable', RESEED, 1) GO -- Build sample data INSERT INTO [TestTable] VALUES ('val') GO -- Select Data SELECT * FROM [TestTable] GO -- Truncate table TRUNCATE TABLE [TestTable] GO -- Build sample data INSERT INTO [TestTable] VALUES ('val') GO -- Select Data SELECT * FROM [TestTable] GO -- Question for you Here -- Clean up DROP TABLE [TestTable] GO Now let us see the output of three of the select statements. 1) First Select after create table 2) Second Select after reseed table 3) Third Select after truncate table The reason is simple: If the table contains an identity column, the counter for that column is reset to the seed value defined for the column. Reference: Pinal Dave (http://blog.sqlauthority.com)       Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • Dualboot 12.04/windows 7 After installation from USB reboot straight to Windows with no option to select ubuntu and no boot loader

    - by Alkatraz
    windows 7 home premium intel i5 2500k CPU ASUSP8Z68-V PRO Motherboard GeForce GTX 570 GPU corsair 120Gb SSD (windows 7 os) WD 1tb HDD I select the USB drive in the BIOS and boot to it and choose install. i select to manually configure partitions, partition the 200gb of unallocated space on my 1Tb HDD into 16Gb swap file 30Gb / extf4 and 154Gb /home extf4. I make sure that the boot loader is installed to corsair 120Gb SSD (where the windows boot is) and installation goes smoothly. When i reboot after install it runs through bios strait into windows. I have tried upwards of a dozen times and i have also tried with linuxmint. I have also redownloaded the ISO and used two different programs to create the live usb. the installation seems to go well as i can see the partitions i have created in the windows device manager after install http://imgur.com/Wp0V1 I currently run lubuntu on my laptop but it is not a dual boot. i'm assuming this is a boot loader issue and i am assuming that inside those partitioned files in my screenshot there is a working OS of ubuntu 12.04 i just have no way of getting to it.

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

    - by Pinal Dave
    In this post titled SQL SERVER – Grouping by Multiple Columns to Single Column as A String we have seen how to group multiple column data in comma separate values in a single row grouping by another column by using FOR XML clause. In this post we will see how we can produce the same result using the GROUP_CONCAT function in MySQL. Let us create the following table and data. CREATE TABLE TestTable (ID INT, Col VARCHAR(4)); 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'; Now to generate csv values of the column col for each ID, use the following code SELECT ID, GROUP_CONCAT(col) AS CSV FROM TestTable GROUP BY ID; The result is ID CSV 1 A,B,C 2 A,B,C,D,E You can also change the delimiters. For example instead of comma, if you want to have a pipe symbol (|), use the following SELECT ID, REPLACE(GROUP_CONCAT(col),',','|') AS CSV FROM TestTable GROUP BY ID; The result is ID CSV 1 A|B|C 2 A|B|C|D|E MySQL makes this very simple with its support of GROUP_CONCAT function. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • How to configure Amazon Security Groups to achieve multi-tier architecture?

    - by ks78
    What is the preferred way to configure Amazon Security Groups to achieve a multi-tier architecture? Each of my instances has its own Security Group, which I only want to use for rules specific to an instance. I'd like to keep any rules which apply to multiple instances in a separate Security Group, which can then be assigned to instance Security Groups as necessary. As an example, I've setup a group called "admin", which allows administrative access from my IP. I added the "admin" group as the source to each of my instance security groups. However, I still can't access the instances from my IP without adding the rules directly to the instance's group. Am I missing something? Although it seems a multi-tier security architecture should be possible, it doesn't seem to be working.

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  • How to configure Amazon Security Groups to achieve multi-tier architecture?

    - by ks78
    What is the preferred way to configure Amazon Security Groups to achieve a multi-tier architecture? Each of my instances has its own Security Group, which I only want to use for rules specific to an instance. I'd like to keep any rules which apply to multiple instances in a separate Security Group, which can then be assigned to instance Security Groups as necessary. As an example, I've setup a group called "admin", which allows administrative access from my IP. I added the "admin" group as the source to each of my instance security groups. However, I still can't access the instances from my IP without adding the rules directly to the instance's group. Am I missing something? Although it seems a multi-tier security architecture should be possible, it doesn't seem to be working.

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  • Blind As a Bat in Multi-Monitor Hell &ndash; Free Program Inside!

    - by ToStringTheory
    If you know me personally, then you probably know that I am going blind thanks to a rare genetic eye disease.  My eye disease has already been a huge detriment to my eyesight.  One of the big things to suffer is my ability to see small things moving fast right in front of me.  On a multi-monitor setup, this makes finding the cursor absolute hell. The Problem I’ll keep this short, as I’ve basically already told you what the problem is.  On my three monitor development computer, I am constantly losing the mouse during the day.  I had used the Microsoft accessibility mousefinder (press CTRL, and it pings around the mouse).  The problem with this is, there is only an effect around 50-100 PX around the mouse, and it is a very light gray, almost unnoticeable.. For someone like me, if I am not looking at the monitor when I click the CTRL button, I have to click it multiple times and dart my eyes back and forth in a futile attempt to catch a glimpse of the action…  I had tried other cursor finders, but none I liked… The Solution So what’s a guy to do when he doesn’t like his options?  MAKE A NEW OPTION…  What else should we as developers do, am I right?  So, I went ahead and made a mousefinder of my own, with 6 separate settings to change the effect.  I am releasing it here for anyone else that may also have problems finding their mouse at times. Some of its features include: Multiple options to change to achieve the exact effect you want. If your mouse moves while it is honing in, it will hone in on its current position. Many times, I would press the button and move my mouse at the same time, and many times, the mouse happened to be at a screen edge, so I would miss it. This program will restart its animation on a new screen if the mouse changes its screen while playing. Tested on Windows 7 x64 Stylish color changing from green to red. Deployed as a ClickOnce, so easy to remove if you don't like it. Press Right CTRL to trigger effect Application lives in notification area so that you can easily reach configuration or close it. To get it to run on startup, copy its application shortcut from its startmenu directory to the “Startup” folder in your startmenu. Conclusion I understand if you don’t download this…  You don’t know me and I don’t know you.  I can only say that I have honestly NOT added any virus’ or malware to the package. Yeah, I know it’s weird Download: ‘ToString(theory) Mousefinder.zip’ CRC32: EEBCE300 MD5: 0394DA581BE6F3371B5BA11A8B24BC91 SHA-1: 2080C4930A2E7D98B81787BB5E19BB24E118991C Finally, if you do use this application - please leave a comment, or email me and tell me what you think of it. Encounter a bug or hashes no longer match? I want to know that too! <warning type=”BadPun”>Now, stop messing around and start mousing around!</warning>

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  • Troubleshooting Blocked Transaction in SQL Server

    - by ChrisD
    While troubleshooting a blocked transaction issue recently, I found this code online.  My apologies in not citing its source, but its lost in my browse history some where.   While the transaction is executing and blocked, open a connection to the database containing the transaction and run the following to return both the SQL statement blocked (the Victim), as well as the statement that’s causing the block (the Culprit)   -- prepare a table so that we can filter out sp_who2 results DECLARE @who TABLE(BlockedId INT, Status VARCHAR(MAX), LOGIN VARCHAR(MAX), HostName VARCHAR(MAX), BlockedById VARCHAR(MAX), DBName VARCHAR(MAX), Command VARCHAR(MAX), CPUTime INT, DiskIO INT, LastBatch VARCHAR(MAX), ProgramName VARCHAR(MAX), SPID_1 INT, REQUESTID INT) INSERT INTO @who EXEC sp_who2 --select the blocked and blocking queries (if any) as SQL text SELECT ( SELECT TEXT FROM sys.dm_exec_sql_text( (SELECT handle FROM ( SELECT CAST(sql_handle AS VARBINARY(128)) AS handle FROM sys.sysprocesses WHERE spid = BlockedId ) query) ) ) AS 'Blocked Query (Victim)', ( SELECT TEXT FROM sys.dm_exec_sql_text( (SELECT handle FROM ( SELECT CAST(sql_handle AS VARBINARY(128)) AS handle FROM sys.sysprocesses WHERE spid = BlockedById ) query) ) ) AS 'Blocking Query (Culprit)' FROM @who WHERE BlockedById != ' .'

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  • Mac OS X multi-user thin client server (terminal server)?

    - by username
    Is there any solution out there to turn a Mac into a true multi-user thin client server? I'd like to set up a few cheap PCs with access to a couple accounts using something like VNC, but it isn't economical to buy a new server for each user or a new license for virtualized OS X Server for each user. I'm fully aware that OS X Server lets you set up users with "network home folders," and I know there's also VNC built into Mac OS X. Neither of these fit the bill (the former requires a thick client, and the latter is single-user only) UPDATE: yay, Lion! http://www.9to5mac.com/54102/10-7-lion-allows-multi-user-remote-computing

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  • how to manage a multi user server on linux?

    - by user1175942
    I'm working on a university project, where I have Tomcat as a web server, and I want to create a multi user environment on top of linux, so every user that logs into my website has his own credentials, and he can access only his own data (files and folders...). The main issue is that the purpose of the website is executing code on the server-side, so I must have a good (reasonable) protection against malicious code. (a user destroying his own user is fine by me) I thought that defining a linux-user for every website-user is the best solution - it isolates each user from the other, and I can define each one's permissions. Can I create users in linux using shell commands? Can I configure max quota/memory/cpu for a user? Anyone has another idea for managing that kind of multi-user environment?

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  • Lock-free multi-threading is for real threading experts...

    - by vdhant
    I was reading through an answer that Jon Skeet gave to a question and in it he mentioned this: As far as I'm concerned, lock-free multi-threading is for real threading experts, of which I'm not one. Its not the first time that I have heard this, but I find very few people talking about how you actually do it if you are interested in learning how to write lock-free multi-threading code. So my question is besides learning all you can about threading, etc where do you start trying to learn to specifically write lock-free multi-threading code and what are some good resources. Cheers

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  • Is it safe to use Select Top and Delete Top in sequence?

    - by Rob Nicholson
    I often write T-SQL loops that look like this While Exists (Select * From #MyTable) Begin Declare @ID int, @Word nvarchar(max) Select Top 1 @ID=ID, @Word=[Word] From #MyTable -- Do something -- Delete #MyTable Where ID=@ID End Works a treat but I noticed the new Delete Top function which would be useful when #MyTable is just a list of strings. In this case, would this work: While Exists (Select * From #MyTable) Begin Declare @Word nvarchar(max) Select Top 1 @Word=[Word] From #MyTable -- Do something -- Delete Top(1) #MyTable End Well yes, it works in my test script but is this safe? Will Select Top 1 and Delete Top(1) always refer to the same record or is Top a little more vague. Thanks, Rob.

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  • SQL: select random row from table where the ID of the row isn't in another table?

    - by johnrl
    I've been looking at fast ways to select a random row from a table and have found the following site: http://74.125.77.132/search?q=cache:http://jan.kneschke.de/projects/mysql/order-by-rand/&hl=en&strip=1 What I want to do is to select a random url from my table 'urls' that I DON'T have in my other table 'urlinfo'.The query I am using now selects a random url from 'urls' but I need it modified to only return a random url that is NOT in the 'urlinfo' table. Heres the query: SELECT url FROM urls JOIN (SELECT CEIL(RAND() * (SELECT MAX(urlid) FROM urls ) ) AS urlid ) AS r2 USING(urlid); And the two tables: CREATE TABLE urls ( urlid INT NOT NULL AUTO_INCREMENT PRIMARY KEY, url VARCHAR(255) NOT NULL, ) ENGINE=INNODB; CREATE TABLE urlinfo ( urlid INT NOT NULL PRIMARY KEY, urlinfo VARCHAR(10000), FOREIGN KEY (urlid) REFERENCES urls (urlid) ) ENGINE=INNODB;

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  • Is there a way to force a user to select an autocomplete value before they can submit the form?

    - by Randy Johnson
    I am using the jqueryui autocomplete feature to allow the user to select their location. I need to make sure they select a location from the autocomplete before they can submit the form. I don't want them to be able to submit the form before they select a value. My solution is after they submit make sure that the value found is in the database. The other solution would be that when they click submit or after they leave the location box and go to another field to submit the entry via ajax to ensure it is valid if not show an error and do not let them submit the form. I was wondering if there was something easier I could do, or if there is something more elegant. I realize they have to be able to type something into the box to get the autocomplete to work, so I could force them to select a value from the autocomplete because it is not a select box, so it seems that my above solutions would be the best way to go. Thoughts?

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  • is it possible to create a multi-project template that references n number of existing projects and

    - by jcollum
    The situation: I need to create about 40+ solutions that all reference 3 projects and have one project that is unique to each one. I'd like to create a multi-project template that does this, but from what I've read it looks like it's very difficult or impossible (related SO question, but doesn't answer). I want my solution to look like this (names changed of course): These three are used by all solutions created under this "family": MyCompany.Extensions MyCompany.MyProject.Tests.Shared MyCompany.MyProject.Scripts This one is the one that makes the solution unique, 123, 124, 125 etc: MyCompany.MyProject.Tests.Unit123 Is it possible to set up a multi-project template that will generate this structure? References: MSDN Create Multi Project Templates

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  • Does the order of the columns in a SELECT statement make a difference?

    - by Frank Computer
    This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

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  • how to select all the data from many tables?

    - by Syom
    how to select all the data from many tables? i try `"SELECT * FROM `table1`, `table2`"` , but result none understandable for me. it returns only some rows from table1, and 3 times all the data from table2. i've red one same question here, but don't understand the answer. so could you help me? thanks in advance. update: when i try (SELECT * FROM `videos`) UNION (SELECT * FROM `users`) it returns #1222 - The used SELECT statements have a different number of columns

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  • Advantage Database Server: slow stored procedure performance.

    - by ie
    I have a question about a performance of stored procedures in the ADS. I created a simple database with the following structure: CREATE TABLE MainTable ( Id INTEGER PRIMARY KEY, Name VARCHAR(50), Value INTEGER ); CREATE UNIQUE INDEX MainTableName_UIX ON MainTable ( Name ); CREATE TABLE SubTable ( Id INTEGER PRIMARY KEY, MainId INTEGER, Name VARCHAR(50), Value INTEGER ); CREATE INDEX SubTableMainId_UIX ON SubTable ( MainId ); CREATE UNIQUE INDEX SubTableName_UIX ON SubTable ( Name ); CREATE PROCEDURE CreateItems ( MainName VARCHAR ( 20 ), SubName VARCHAR ( 20 ), MainValue INTEGER, SubValue INTEGER, MainId INTEGER OUTPUT, SubId INTEGER OUTPUT ) BEGIN DECLARE @MainName VARCHAR ( 20 ); DECLARE @SubName VARCHAR ( 20 ); DECLARE @MainValue INTEGER; DECLARE @SubValue INTEGER; DECLARE @MainId INTEGER; DECLARE @SubId INTEGER; @MainName = (SELECT MainName FROM __input); @SubName = (SELECT SubName FROM __input); @MainValue = (SELECT MainValue FROM __input); @SubValue = (SELECT SubValue FROM __input); @MainId = (SELECT MAX(Id)+1 FROM MainTable); @SubId = (SELECT MAX(Id)+1 FROM SubTable ); INSERT INTO MainTable (Id, Name, Value) VALUES (@MainId, @MainName, @MainValue); INSERT INTO SubTable (Id, Name, MainId, Value) VALUES (@SubId, @SubName, @MainId, @SubValue); INSERT INTO __output SELECT @MainId, @SubId FROM system.iota; END; CREATE PROCEDURE UpdateItems ( MainName VARCHAR ( 20 ), MainValue INTEGER, SubValue INTEGER ) BEGIN DECLARE @MainName VARCHAR ( 20 ); DECLARE @MainValue INTEGER; DECLARE @SubValue INTEGER; DECLARE @MainId INTEGER; @MainName = (SELECT MainName FROM __input); @MainValue = (SELECT MainValue FROM __input); @SubValue = (SELECT SubValue FROM __input); @MainId = (SELECT TOP 1 Id FROM MainTable WHERE Name = @MainName); UPDATE MainTable SET Value = @MainValue WHERE Id = @MainId; UPDATE SubTable SET Value = @SubValue WHERE MainId = @MainId; END; CREATE PROCEDURE SelectItems ( MainName VARCHAR ( 20 ), CalculatedValue INTEGER OUTPUT ) BEGIN DECLARE @MainName VARCHAR ( 20 ); @MainName = (SELECT MainName FROM __input); INSERT INTO __output SELECT m.Value * s.Value FROM MainTable m INNER JOIN SubTable s ON m.Id = s.MainId WHERE m.Name = @MainName; END; CREATE PROCEDURE DeleteItems ( MainName VARCHAR ( 20 ) ) BEGIN DECLARE @MainName VARCHAR ( 20 ); DECLARE @MainId INTEGER; @MainName = (SELECT MainName FROM __input); @MainId = (SELECT TOP 1 Id FROM MainTable WHERE Name = @MainName); DELETE FROM SubTable WHERE MainId = @MainId; DELETE FROM MainTable WHERE Id = @MainId; END; Actually, the problem I had - even so light stored procedures work very-very slow (about 50-150 ms) relatively to plain queries (0-5ms). To test the performance, I created a simple test (in F# using ADS ADO.NET provider): open System; open System.Data; open System.Diagnostics; open Advantage.Data.Provider; let mainName = "main name #"; let subName = "sub name #"; // INSERT let cmdTextScriptInsert = " DECLARE @MainId INTEGER; DECLARE @SubId INTEGER; @MainId = (SELECT MAX(Id)+1 FROM MainTable); @SubId = (SELECT MAX(Id)+1 FROM SubTable ); INSERT INTO MainTable (Id, Name, Value) VALUES (@MainId, :MainName, :MainValue); INSERT INTO SubTable (Id, Name, MainId, Value) VALUES (@SubId, :SubName, @MainId, :SubValue); SELECT @MainId, @SubId FROM system.iota;"; let cmdTextProcedureInsert = "CreateItems"; // UPDATE let cmdTextScriptUpdate = " DECLARE @MainId INTEGER; @MainId = (SELECT TOP 1 Id FROM MainTable WHERE Name = :MainName); UPDATE MainTable SET Value = :MainValue WHERE Id = @MainId; UPDATE SubTable SET Value = :SubValue WHERE MainId = @MainId;"; let cmdTextProcedureUpdate = "UpdateItems"; // SELECT let cmdTextScriptSelect = " SELECT m.Value * s.Value FROM MainTable m INNER JOIN SubTable s ON m.Id = s.MainId WHERE m.Name = :MainName;"; let cmdTextProcedureSelect = "SelectItems"; // DELETE let cmdTextScriptDelete = " DECLARE @MainId INTEGER; @MainId = (SELECT TOP 1 Id FROM MainTable WHERE Name = :MainName); DELETE FROM SubTable WHERE MainId = @MainId; DELETE FROM MainTable WHERE Id = @MainId;"; let cmdTextProcedureDelete = "DeleteItems"; let cnnStr = @"data source=D:\DB\test.add; ServerType=local; user id=adssys; password=***;"; let cnn = new AdsConnection(cnnStr); try cnn.Open(); let cmd = cnn.CreateCommand(); let parametrize ix prms = cmd.Parameters.Clear(); let addParam = function | "MainName" -> cmd.Parameters.Add(":MainName" , mainName + ix.ToString()) |> ignore; | "SubName" -> cmd.Parameters.Add(":SubName" , subName + ix.ToString() ) |> ignore; | "MainValue" -> cmd.Parameters.Add(":MainValue", ix * 3 ) |> ignore; | "SubValue" -> cmd.Parameters.Add(":SubValue" , ix * 7 ) |> ignore; | _ -> () prms |> List.iter addParam; let runTest testData = let (cmdType, cmdName, cmdText, cmdParams) = testData; let toPrefix cmdType cmdName = let prefix = match cmdType with | CommandType.StoredProcedure -> "Procedure-" | CommandType.Text -> "Script -" | _ -> "Unknown -" in prefix + cmdName; let stopWatch = new Stopwatch(); let runStep ix prms = parametrize ix prms; stopWatch.Start(); cmd.ExecuteNonQuery() |> ignore; stopWatch.Stop(); cmd.CommandText <- cmdText; cmd.CommandType <- cmdType; let startId = 1500; let count = 10; for id in startId .. startId+count do runStep id cmdParams; let elapsed = stopWatch.Elapsed; Console.WriteLine("Test '{0}' - total: {1}; per call: {2}ms", toPrefix cmdType cmdName, elapsed, Convert.ToInt32(elapsed.TotalMilliseconds)/count); let lst = [ (CommandType.Text, "Insert", cmdTextScriptInsert, ["MainName"; "SubName"; "MainValue"; "SubValue"]); (CommandType.Text, "Update", cmdTextScriptUpdate, ["MainName"; "MainValue"; "SubValue"]); (CommandType.Text, "Select", cmdTextScriptSelect, ["MainName"]); (CommandType.Text, "Delete", cmdTextScriptDelete, ["MainName"]) (CommandType.StoredProcedure, "Insert", cmdTextProcedureInsert, ["MainName"; "SubName"; "MainValue"; "SubValue"]); (CommandType.StoredProcedure, "Update", cmdTextProcedureUpdate, ["MainName"; "MainValue"; "SubValue"]); (CommandType.StoredProcedure, "Select", cmdTextProcedureSelect, ["MainName"]); (CommandType.StoredProcedure, "Delete", cmdTextProcedureDelete, ["MainName"])]; lst |> List.iter runTest; finally cnn.Close(); And I'm getting the following results: Test 'Script -Insert' - total: 00:00:00.0292841; per call: 2ms Test 'Script -Update' - total: 00:00:00.0056296; per call: 0ms Test 'Script -Select' - total: 00:00:00.0051738; per call: 0ms Test 'Script -Delete' - total: 00:00:00.0059258; per call: 0ms Test 'Procedure-Insert' - total: 00:00:01.2567146; per call: 125ms Test 'Procedure-Update' - total: 00:00:00.7442440; per call: 74ms Test 'Procedure-Select' - total: 00:00:00.5120446; per call: 51ms Test 'Procedure-Delete' - total: 00:00:01.0619165; per call: 106ms The situation with the remote server is much better, but still a great gap between plaqin queries and stored procedures: Test 'Script -Insert' - total: 00:00:00.0709299; per call: 7ms Test 'Script -Update' - total: 00:00:00.0161777; per call: 1ms Test 'Script -Select' - total: 00:00:00.0258113; per call: 2ms Test 'Script -Delete' - total: 00:00:00.0166242; per call: 1ms Test 'Procedure-Insert' - total: 00:00:00.5116138; per call: 51ms Test 'Procedure-Update' - total: 00:00:00.3802251; per call: 38ms Test 'Procedure-Select' - total: 00:00:00.1241245; per call: 12ms Test 'Procedure-Delete' - total: 00:00:00.4336334; per call: 43ms Is it any chance to improve the SP performance? Please advice. ADO.NET driver version - 9.10.2.9 Server version - 9.10.0.9 (ANSI - GERMAN, OEM - GERMAN) Thanks!

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  • How can I stop SQL Server Management Studio replacing 'SELECT *' with the column list ?

    - by Ben McIntyre
    SQL Server Mgmt Studio is driving me crazy. If I create a view and SELECT '*' from a table, it's all OK and I can save the view. Looking at the SQL for the view (eg.by scripting a CREATE) reveals that the 'SELECT *' really is saved to the view's SQL. But as soon as I reopen the view using the GUI (right click modify), SELECT * is replaced with a column list of all the columns in the table. How can I stop Management Studio from doing this ? I want my 'SELECT *' to remain just that. Perhaps it's just the difficulty of googling 'SELECT *' that prevented me from finding anything remotely relevant to this (i did put it in double quotes). Please, I am highly experienced in Transact-SQL, so please DON'T give me a lecture on why I shouldn't be using SELECT *. I know all the pros and cons and I do use it at times. It's a language feature, and like all language features can be used for good or evil (I emphatically do NOT agree that it is never appropriate to use it). Edit: I'm giving Marc the answer, since it seems it is not possible to turn this behaviour off. Problem is considered closed. I note that Enterprise Manager did no similar thing. The workaround is to either edit SQL as text, or go to a product other than Managment Studio. Or constantly edit out the column list and replace the * every time you edit a view. Sigh.

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  • Best way to randomly select columns from random rows of SQL results.

    - by LesterDove
    A search of SO yields many results describing how to select random rows of data from a database table. My requirement is a bit different, though, in that I'd like to select individual columns from across random rows in the most efficient/random/interesting way possible. To better illustrate: I have a large Customers table, and from that I'd like to generate a bunch of fictitious demo Customer records that aren't real people. I'm thinking of just querying randomly from the Customers table, and then randomly pairing FirstNames with LastNames, Address, City, State, etc. So if this is my real Customer data (simplified): FirstName LastName State ========================== Sally Simpson SD Will Warren WI Mike Malone MN Kelly Kline KS Then I'd generate several records that look like this: FirstName LastName State ========================== Sally Warren MN Kelly Malone SD Etc. My initial approach works, but it lacks the elegance that I'm hoping the final answer will provide. (I'm particularly unhappy with the repetitiveness of the subqueries, and the fact that this solution requires a known/fixed number of fields and therefore isn't reusable.) SELECT FirstName = (SELECT TOP 1 FirstName FROM Customer ORDER BY newid()), LastName= (SELECT TOP 1 LastNameFROM Customer ORDER BY newid()), State = (SELECT TOP 1 State FROM Customer ORDER BY newid()) Thanks!

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  • What is happening in this T-SQL code? (Concatenting the results of a SELECT statement)

    - by Ben McCormack
    I'm just starting to learn T-SQL and could use some help in understanding what's going on in a particular block of code. I modified some code in an answer I received in a previous question, and here is the code in question: DECLARE @column_list AS varchar(max) SELECT @column_list = COALESCE(@column_list, ',') + 'SUM(Case When Sku2=' + CONVERT(varchar, Sku2) + ' Then Quantity Else 0 End) As [' + CONVERT(varchar, Sku2) + ' - ' + Convert(varchar,Description) +'],' FROM OrderDetailDeliveryReview Inner Join InvMast on SKU2 = SKU and LocationTypeID=4 GROUP BY Sku2 , Description ORDER BY Sku2 Set @column_list = Left(@column_list,Len(@column_list)-1) Select @column_list ---------------------------------------- 1 row is returned: ,SUM(Case When Sku2=157 Then Quantity Else 0 End) As [157 -..., SUM(Case ... The T-SQL code does exactly what I want, which is to make a single result based on the results of a query, which will then be used in another query. However, I can't figure out how the SELECT @column_list =... statement is putting multiple values into a single string of characters by being inside a SELECT statement. Without the assignment to @column_list, the SELECT statement would simply return multiple rows. How is it that by having the variable within the SELECT statement that the results get "flattened" down into one value? How should I read this T-SQL to properly understand what's going on?

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