O Martin Marques έγραψε στις Sep 28, 2004 :
> I have a bunch of queries in a system I'm finishing, and I bumped with a > question on performace. > Which is the best way to solve this: > > I need to know if there is at least one row in the relation that comes from a > determinated query. Which is the best way to do this: > > (a) Build the query with "SELECT * ..." and after executing the query see if > numRows()>0 > (b) Build the query with "SELECT count(*) ...", fetch the row and see if > count>0 You could also try (c) SELECT exists (select 1 ... limit 1) and test the boolean value in the one and only row returned, where "..." is your clause as in (a),(b). > > I'm working with (a) because I see it better in performace, but I wanted to be > sure the numRows() will actually give me the exact amount of rows (had some > problems in the past with Informix). > > The aplication is written in PHP. > > -- -Achilleus ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
