Обсуждение: When are subqueries needed

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When are subqueries needed

От
Bruce Momjian
Дата:
Can someone summarize when subqueries are required.  I thought
aggregates often needed them, but I see now that table aliases can do it
in most cases.  I think NOT IN can not be done without subqueries.

Is there a general rule on this?  A rule about correlated subqueries?

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