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SQL Subquery

A subquery is a SELECT nested inside another statement, usable as a scalar value, a row filter (IN, EXISTS), or a derived table in FROM. It lets one query's result parameterize another within a single statement.

Questions this Concept answers

Why can rewriting a subquery as a join change a query's speed so much?

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SQL Subquery (Visually Explained) | Complete Guide with Correlated Subquery | #SQL Course 27

A subquery is a query nested inside another query, whose result exists only as an intermediate relation local to the enclosing (main or outer) query and is discarded once execution completes; it supp…