Press "Enter" to skip to content

Optimizing for Mediocre

Erik Darling is always optimal:

Using the OPTIMIZE FOR UNKNOWN hint, or declaring variables inside of a code block to be used in a where clause have the same issue, though: they make SQL Server’s query optimizer make bad guesses, which often lead to bad execution plans.

You can read great detail about that here.

Read on for a bit of a deserved rant and an example to show why OPTIMIZE FOR UNKNOWN often doesn’t solve the problem.