Re: (How) are subqueries optimized involving the same table?

[Bob Field]

Prefix the query with EXPLAIN and you will get back a resultset detailing what operations are performed. Personally I would expect caching to be a benefit here since it is the same row returned each time.

I think you'd be better off with something like this:

SELECT t1.foo, t1.field1, t1.field2, t1.field3
FROM t1
JOIN t2 ON t2.id = 123
WHERE t1.id = 7;

Or even:

SELECT field1, field2, field3 INTO @f1, @f2, @f3 FROM t2 WHERE id = 123;
SELECT foo, @f1, @f2, @f3 FROM t1 WHERE id = 7;

(Assuming the same connection, i.e. not from Query Browser)



Edited 1 time(s). Last edit at 07/13/2006 08:13AM by Bob Field.