Re: Query never finishes

[Peter Brawley]

> identify which objects are in table A that are not in table B

`a` left join `b` requires that all join-relevant values in `a` be examined. Run Explain Extended on your query to see what if any index the optimiser can find for the left side.

If you can't speed your query up, there's probably something wrong with your setup. Until you fix that, you can fiddle a workaround: give `a` and `b` auto_increment primary keys, then ...

create table a_in_b
select a.pk
from a
join b on a.val1=b.vala;

Now the primary key values which are in `a` and not in `a_in_b` are the pks of your unmatched rows.