T-SQL

When I do performance tuning for clients, I really pride myself on making as few changes as possible in order to make a tremendous difference. I consider it a failure when I have to tell someone to rewrite a bunch of queries from scratch. However, there are some cases where I just can’t work around…

When we think about building dynamic SQL, we usually think about a stored procedure like this that takes input parameters, builds a string, and then executes that string. Here’s a simple example: Transact-SQL CREATE OR ALTER PROC dbo.usp_SearchUsers @SearchDisplayName NVARCHAR(40) = NULL, @SearchLocation NVARCHAR(100) = NULL, @SearchReputation INT = NULL AS BEGIN DECLARE @StringToExecute NVARCHAR(4000);…

Say we have a stored procedure that queries the Stack Overflow database. We have two separate parameters, @DisplayName and @Location, so folks can search for people by name, location, or both. For performance reasons, we decide to build dynamic SQL: Transact-SQL CREATE OR ALTER PROC dbo.UserSearch @DisplayName NVARCHAR(40) = NULL, @Location NVARCHAR(100) = NULL AS…

You Shoulda Brought A Bigger Int Sometimes you run a query, and everything goes fine. For a while. For example, if I run this query in the 2010 copy of Stack Overflow, it finishes pretty quickly, and without error. Transact-SQL SELECT u.Id, u.DisplayName, SUM(p.Score) AS SumPostScore, AVG(c.Score) AS SumCommentScore FROM dbo.Users AS u JOIN dbo.Posts…

Hell Here! Get Your Fresh Hell, Here! Let’s face it — as far as developer tools go, SSMS is pretty bad. Intellisense? The jokes write themselves. Don’t get me wrong, SSMS is a good management tool, but it’s not a good development tool (and what kind of maniac sticks debug — F6 — next to execute —…

Method 1, Bad: ORDER BY NEWID() Easy to write, but it performs like hot, hot garbage because it scans the entire clustered index, calculating NEWID() on every row: The plan with the scan That took 6 seconds on my machine, going parallel across multiple threads, using tens of seconds of CPU for all that computing…

Yello! Transact-SQL SELECT ISNUMERIC('$') AS [What] UNION ALL SELECT ISNUMERIC('£') AS [What] UNION ALL SELECT ISNUMERIC(',') AS [What] UNION ALL SELECT ISNUMERIC('.') AS [What] UNION ALL SELECT ISNUMERIC('0e+99') AS [What] UNION ALL SELECT ISNUMERIC('2e2') AS [What] UNION ALL SELECT ISNUMERIC('12D4') AS [What] UNION ALL SELECT ISNUMERIC(',1,1,1,1,1,1,1') AS [What] UNION ALL SELECT ISNUMERIC('-') AS [What] UNION…

Using the Stack Overflow public export, take these two queries looking for a particular user by Id (the clustering key): Transact-SQL SELECT * FROM dbo.Users WHERE Id = 26837; SELECT * FROM dbo.Users WHERE Id LIKE 26837; 12 SELECT * FROM dbo.Users WHERE Id = 26837;SELECT * FROM dbo.Users WHERE Id LIKE 26837; The first…

Virtualization used to be a really Big Deal™ for database admins: we had to do a lot of careful planning to get a virtualization project done right. These days, virtualization is more and more of a no-brainer: most apps make the transition just fine. Every now and then, though, an exception pops up – usually…

For this month’s T-SQL Tuesday, Ewald asked who’s made a difference in our careers. When I first got started out in SQL Server, all I had was books and Books Online. Back then, neither of them were particularly well-indexed, nor were they up to date. Then I found a web site that turned things around.…