Carrying Baggage Through Query Plans: Why Wide Queries Get Heavy

I see this pattern repeatedly: a “wide” query that returns many columns and less than 100k rows runs slowly. SQL Server gets slow when it drags large amounts of baggage through the entire query plan, like a solo traveler struggling with massive suitcases in an airport instead of picking them up close to their destination.

SQL Server often minimizes data access by grabbing all the columns it needs early in query execution, then doing joins and filters. This means presentation columns get picked up early.

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Msg 195: STRING_SPLIT Is Not a Recognized Built-In Function Name

Yesterday, I was writing some Transact SQL to dust off the cobwebs. I got confused when I was playing around with the STRING_SPLIT function, and kept getting the error:

Msg 195, Level 15, State 10, Line 2
'STRING_SPLIT' is not a recognized built-in function name.

I checked my database compatibility level, which must be 130 or higher for the function to be available. My database compatibility level was 160, so that was fine.

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CROSS APPLY in T-SQL: Why to APPLY

Michelle asked a great question:

In your own words, why would one want to use a cross apply operator rather than a join operator? I’m old school, and I’m just not getting why a cross apply would be so much better to use than a join.

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Using APPLY for calculations

Here’s a little TSQL snack. I picked this up in a presentation by Itzik Ben-Gan at the PNWSQL user group recently, and it’s become a fast favorite.

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