Re: how sub queries and joins differs funcationally

Hi shreedhar :

--- shreedhar <shreedhar(at)lucidindia(dot)net> wrote:
> Can any body tell that how sub queries and joins
> differs funcationally.
> Because sub queries taking lot of time than joins.
>
The following could be the probable reasons:
a) Your are using correlated queries - Correlated
queries always re-evaluate the sub-query for each row
processed.
b) You have an IN clause - try using EXISTS clause,
since it IN clause doesn't utilize the index when your
subquery is another SELECT statement.

ludwig.

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