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SubQueries

A Select statement within another SELECT, INSERT, UPDATE or DELETE statement. Subqueries can produce the same results as Joins. But Subqueries are more recommandable than Joins and will take less IO cycles than joins.,


Remember:

1) One can have as many nested subqueries in one as one want, there is no limit on this.

2) The subquery is always enclosed in parentheses unless used in Update statement.

3) Subquery can not contain an Order By, Compute, or SELECT INTO Clause ie in Where list!!

4) Subquery can not be used in the Order By clause.

Example:

Sql> SELECT distinct au_fname,au_lname, state

FROM authors where state IN

(SELECT state from stores);

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