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From: Stut (stuttlegmail.com)
Date: Sun Nov 25 2007 - 07:50:21 CST
David T. Ashley wrote:
> I have a table with two integer fields (call them p and q).
> When I insert a record with a known p, I want to choose q to be one larger
> than the largest q with that p.
> What is the best and most efficient way to do this?
> For example, let's say the table contains (p,q):
> If I insert a new record with p=2, I would want to choose q to be 6. But if
> I insert a record with p=3, I would want to choose q to be 3.
> Is there any alternative to locking the table, querying for max q with the
> desired p, then inserting?
insert into test1 set p = 2, q = (select max(q) + 1 from test1 as tmp
where p = 2)
Probably not very efficient, but it works.
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