subquery – sqlsunday.com

The uncorrelated correlated subquery

I’ve seen this accidental pattern more times than I care to remember, and it still bothers me no end. There’s a valuable lesson to be had at the end, though.

Using DELETE on subqueries and common table expressions

Here’s an interesting feature I found in the code of a colleague the other day. A common task in T-SQL is eliminating duplicate records. This became a lot easier with the introduction of windowed functions way back in SQL Server 2005, such as ROW_NUMBER(), but it turns out, I’ve still been missing out on a really simple and cool solution.