T-SQL Tuesday #25 - Tips and Tricks
13 December 2011
It is T-SQL Tuesday once again, hosted by Allen White (b / t). The theme for this T-SQL Tuesday is Tricks.
One of my favorite tricks is to use INTERSECT when I have to rewrite a SELECT query, to make sure I am returning the same data.
Let’s say I have a slow query that returns 1640 rows:
I refactor it for speed, and make sure it still returns 1640 rows:
How am I sure my new query returns the same data? I use INTERSECT, and make sure the intersect-ed query returns the same number of rows as the original query:
“Success is concrete. Just like the Mafia.”
Now I know my changes have not affected what data is returned. Success!
I also have a more concrete example, using the AdventureWorks2008 R2 database, and Example.sql .