I agree with Brian, a stored procedure or function seems to be the way to go, where you get the value, store it in a variable, and then use the variable in the query.
On Thu, Jul 19, 2012 at 10:29 AM, Brian Leach <[email protected]>wrote: > George > > It depends on the db type. In SQL Server, for example, you would create a > stored procedure that would capture the subquery result to a local variable > and use that. > > e.g. > > DECLARE @lastUpdate DATETIME; > SELECT @lastUpdate = some_expression ; > select * from table where last_update > @lastUpdate > > But I don't know with mySQL - it's a bit short on intellect - but I see it > has a SELECT .. INTO format for populating a variable. Might be worth a > shot. > > > Brian > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of George Gallen > Sent: 19 July 2012 16:56 > To: U2 Users > Subject: [U2] MySQL query qestion.... > > This is specific to MySQL, but could apply to any SQL DB. > > Is there a way to put the results of one query to be used by another, > without having that second query run on each Iteration of the sub query? > > Example: > > SELECT * FROM TABLE WHERE LAST_UPDATE > (SELECT UPDATE_PROCEDURE()); > > The function UPDATE_PROCEDURE() returns a timestamp, and then updates > itself > with a new timestamp. > > My workaround is: > > SELECT * FROM TABLE WHERE LAST_UPDATE > (SELECT GET_PROCEDURE()); SELECT > UPDATE_PROCEDURE(); > > Here the GET_PROCEDURE() only retrieves a value, and doesn't update it. > > BUT...if there were half a million records in the TABLE, I'd prefer not to > run the GET procedure half a million times > To retrieve the same result which could add significant processing time > (this would be run for each of the tables > I'm mirroring on UV from MySQL . > > George > > > _______________________________________________ > U2-Users mailing list > [email protected] > http://listserver.u2ug.org/mailman/listinfo/u2-users > > > _______________________________________________ > U2-Users mailing list > [email protected] > http://listserver.u2ug.org/mailman/listinfo/u2-users > _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users
