Friends --
One of my associates came up to me Friday with a question. It seemed easy
enough. I mean, I've been doing stuff like this for years. The question
was, "I have duplicate ids here, some with X field null, some without. I
want to get rid of all the duplicates where X field is not null." Fine.
Standard correlated subquery.
delete from <tablename> a
where rowid not in (select min(rowid)
where pid=a.pid
and X is not null)
and X is not null
Right?
So, my associate says "what are you doing? you're going to go through the
table every single time for each record?" Why, yes, that is indeed what I'm
doing here. "Why don't you just open a cursor and delete that way?" says my
associate...
select pid
from <tablename>
where X is not null
group by pid
having count(*) > 1
{
skip one
delete the rest
}
"But," I tell my associate, "you still have to go to the table to get
information on which records to delete. You can't do this without a
correlated subquery."
Yes, he assures me, there *has* to be a way.
OK. Maybe I've just been doing things the same way for too long. I'm
willing to cop to that. Can anybody out there come up with a way to do this
relatively normal operation without a correlated subquery?
Bambi.
--
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--
Author: Bellow, Bambi
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