Re: Outer joins = full scan?

Ed Prochak wrote:

> Why do you want to use an index on the outer join query??
>
> Think about what an OUTER JOIN is requesting the DB to do: return ALL rows
> of the base table (T), matched or not with the rows of the outer table
> (C).
>
> What is the fastest way to get all the rows of the table?
>
> A) access the index and then access the table
> B) access just the table
>
> Answer B is faster for accessing all rows of the table.

True, but not in this case Ed.

He uses criteria in his statement on table T (table 1 in the outer join). Thus is it not requested all rows from table T.

I.e.
> AND t.location_code = 'value'
> AND t.case_num = 'value';

This could be faster using an index than a full table scan.

--
Billy