What are the issues related with correlated subqueries?

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Krishna
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What are the issues related with correlated subqueries?

Post by Krishna » Sun Mar 29, 2009 10:21 pm

What are the issues related with correlated subqueries?

Sukanthi Darwin
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Post by Sukanthi Darwin » Sun Nov 22, 2009 8:43 pm

Correlated subselects are often resource-intensive because the subselect is evaluated for each qualifying value in the outer select. When compared to JOIN, the WHERE predicate is evaluated in Stage 1, thus reducing the rows passed to Stage 2 and the correlated predicate is evaluated in Stage 2.

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