11.4K
REInterviewer: When should you avoid using window functions?
Most people think window functions are always better.
They are powerful.
But power without judgment is dangerous.
Avoid them when a simple GROUP BY can solve the problem.
Avoid them when the dataset is huge and sorting becomes expensive.
Avoid them when indexing can give you a faster aggregate result.
Avoid them when you don’t actually need row-level detail.
Window functions shine when you need both aggregate and row data together.
But if you only need one summary row per group, keep it simple.
Good SQL developers know window functions.
Great SQL developers know when not to use them.
Performance is a thinking skill, not a syntax trick.
@rebellionrider
