Hi folks,
This will be simple for the experts, I hope. I have two tables,
one of which, "A" has an ID field, and another of which, "B" is a
join table which references A.ID.
I want to delete from "A" all items which are not currently
represented in B. I could use this SQL I think, but I'm conscious
of how SLOOOOOOW it would be, because the second query is
going to be run for EVERY row in A. Can anyone propose a more
efficient formulation please?
delete from A
where ID not in
(select A.ID from A, B
where B.A_ID=A.ID)
cheers,
peter
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Peter Hyde, SPIS Ltd, Christchurch, New Zealand
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