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gnanasekar
Starting Member
6 Posts |
 Posted - 2011-08-09 : 08:25:17
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| can u explain difference between correlated subquery vs sub query in my interview i explain like thisIn sub query the inner query is executed only once. Depeding upon the results of inner query , outer query is evaluated.In correlated subquery the inner query is evaluated once for each row processed by the parent statement or outer query.LIKE THIS THEY R NOT SATISFY MY ANS SO PLZ EXPLAIN IT |
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Ghanta
Yak Posting Veteran
96 Posts |
Posted - 2011-08-09 : 09:31:58
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If you google it you will get all the info; however, your definition looks good.quote:
Originally posted by gnanasekar
can u explain difference between correlated subquery vs sub query in my interview i explain like thisIn sub query the inner query is executed only once. Depeding upon the results of inner query , outer query is evaluated.In correlated subquery the inner query is evaluated once for each row processed by the parent statement or outer query.LIKE THIS THEY R NOT SATISFY MY ANS SO PLZ EXPLAIN IT
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GilaMonster
Master Smack Fu Yak Hacker
4507 Posts |
Posted - 2011-08-09 : 10:16:09
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quote:
Originally posted by gnanasekar
In correlated subquery the inner query is evaluated once for each row processed by the parent statement or outer query.
It is not, and it's trivial to test and see that a correlated subquery does not necessarily run once for each row of the outer query. There are two special cases where it does, but the majority of the time it does not.The actual definition of a correlated subquery is a subquery that contains a reference to a column in the outer query. --Gail ShawSQL Server MVP |
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explain subquery vs correlated subquery