finding items with 0 rels for a 0 to many relationship

[danmcb <danielmcbrearty@xxxxxxxxx>]

Hi

I have two tables, say A and B,  that have a many-to-many
relationship, implemented in the usual way with a join table A_B.

How can I economically find all the rows in table A whose id's are not
in A_B at all (i.e. they have zero instances of B associated)?

Thanks

Daniel