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Using LIKE on Integers Gets You Implicit Conversion

Brent Ozar
T-SQL
5 Comments
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…
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Two Code Patterns That Don’t Virtualize Well

Brent Ozar
T-SQL
13 Comments
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…
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SQL Server Workarounds

Erik Darling
Development, SQL Server, T-SQL
14 Comments
360 Questions We’ve been asking you folks a lot about what you’d add to SQL Server, and we’ve gotten some great answers. There are even some that have been answered in the last couple versions of SQL Server. For instance, 2016 brought us STRING_SPLIT! SQL Server 2017 has a whole bunch of neat stuff: CONCAT_WS…
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Bad Idea Jeans: Multiple Index Hints

Erik Darling
Bad Idea Jeans, T-SQL
5 Comments
I hate that you can do this Here’s the thing: I’m mostly writing this because I didn’t know you could do it. But it’s cool, because it’ll reinforce some other concepts, and I’ll show you why you shouldn’t do it. I’m talking, of course, about index hints. To be more specific, hinting multiple indexes on…
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Don’t Use Scalar Functions in Views.

Erik Darling
T-SQL
3 Comments
The short story: if your view has a scalar user-defined function it it, any query that calls the view will go single-threaded, even if the query doesn’t reference the scalar function. Now for the long story. Quite often people will inherit and rely on views written back in the dark ages, before people were aware…
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Replacing ISNULL In A WHERE Clause

Erik Darling
Execution Plans, T-SQL
4 Comments
I like blogging Really, I do. But sometimes I like a change of pace. Instead of blogging about this question, I posted it over on dba.stackexchange.com. Also, I thought it was an interesting question, and apparently many other people agreed. Not just because I wanted some more points, but because blog comments are notoriously sucky…
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The Surprising Behavior of Trailing Spaces

Brent Ozar
T-SQL
27 Comments
In every training class we do, I learn stuff from students. Here’s last week’s surprise. Create a temp table, and put in a value with trailing spaces. Then query for it using the = and <> operators, using different numbers of trailing spaces: Transact-SQL CREATE TABLE #Wines (Winery VARCHAR(50)); INSERT INTO #Wines VALUES ('Cliff Lede…
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Fun With Logging Dynamic SQL

Erik Darling
T-SQL
9 Comments
While working on a demo I thought this might make a fun aside to share on the blog, because working with dynamic SQL can be challenging. Especially if you don’t have a monitoring tool or application profiling to figure out who ran what and when, most of the time you’ll have no idea what went…
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A Little Fun With Math

Erik Darling
SQL Server, T-SQL
5 Comments
I’ve never been much at math But I’ve always liked reading about it. It’s super interesting, and it always blows my mind. Like, guaranteed. Once in a while I’ll even try my hand at solving problems I read about in SQL. Not because SQL is a particularly good language for it; but just because sometimes…
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Tara Kizer

What TRY/CATCH Doesn’t Handle

Tara Kizer
SQL Server, T-SQL
25 Comments
We were once asked in class what TRY/CATCH doesn’t handle besides object existence errors. It’s well documented in Books Online (BOL). If you’re like me, then tl;dr. Are we even calling it Books Online these days? I still say “bookmark lookup” instead of “key lookup”. I suppose I’ll be saying Books Online for quite some…
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