On Feb 23, 2009, at 1:39 PM, John Elrick wrote: > A clarification question...given the query: > > create table x (x_id integer, f varchar); > create table y (y_id integer, x_id integer, f varchar); > > insert into x values(1, 'wibble'); > insert into y values(1, 1, 'foo'); > insert into y values(1, 1, 'bar'); > > select y.y_id, case when y.f = 'foo' then 'very good' else (select x.f > from x where x.x_id = y.x_id) end from y > > The documentation states that: > > "If the SELECT expression does contain variables from the outer query, > then the SELECT is reevaluated every time it is needed." > > Am I correct in assuming that if (using the above example) y.f = 'foo' > that the sub-select is considered "not needed" and therefore is not > executed? >
I think that is what it does. It is clearly what it ought to do. You can double check by doing an EXPLAIN and examining the generated code to make sure the subquery is skipped completely when y.f=='foo'. > > John Elrick > Fenestra Technologies > > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users D. Richard Hipp d...@hwaci.com _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
