SQL: The difference between WHERE and HAVING

Re:SQL: The difference between WHERE and HAVING by tgv on Tuesday December 14, 2021 @08:55AM (#29551483)

I don't think HAVING is strictly needed, but you need to use a sub-query.

   SELECT x ... HAVING y => SELECT * FROM (x ...) t WHERE y

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Re:SQL: The difference between WHERE and HAVING by throwawayffffas on Tuesday December 14, 2021 @09:03AM (#29551559)

Yeah, you are correct it's really just syntactic sugar for that. As another comment points out, WHERE and HAVING are just σ in relational algebra.

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Re:SQL: The difference between WHERE and HAVING by maweki on Tuesday December 14, 2021 @09:43AM (#29552025)

In that sense, HAVING and WHERE being different is basically a "free" subquery without allowing subqueries.

One inner σ (WHERE) and one outer σ (HAVING).

If subqueries are allowed, then you don't need that.

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Re:SQL: The difference between WHERE and HAVING by FedericoRazzoli on Tuesday December 14, 2021 @12:50PM (#29554694)

You are correct, HAVING is essentially syntax sugar. But to be fair, I'm glad it exists.

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Re:SQL: The difference between WHERE and HAVING by tgv on Tuesday December 14, 2021 @12:59PM (#29554844)

Sure, and I remember the version of mySQL that didn't have sub-queries. Having HAVING has your back, then.

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