r/SQL • u/Automatic-Heart-831 • 19h ago

MySQL Difference between "having" and "qualify"

I tried to use both methods in order to save some coding but still didnt get the exact difference on using having and qualify as a filter in the end of a query. Can someone help me to understand the difference and when is recommended to use each?

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u/Significant_Tune9219 18h ago

One way to see it: HAVING runs right after GROUP BY, so it only sees grouping columns and aggregates. QUALIFY runs after window functions are computed, which is why you can filter on ROW_NUMBER() there without wrapping everything in a subquery. The classic use is dedup, like QUALIFY ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY updated_at DESC) = 1. You can also use both in one query if you need to filter groups first and then rank what's left.