On 2004-12-02, Tom Lane <[EMAIL PROTECTED]> wrote: > "Kevin B." <[EMAIL PROTECTED]> writes: >> Select a.i, b.i >> from t as a >> left join t as b on a.i = b.i >> where a.n = 'a' and b.n = 'b' and b.i is null > > This can't succeed since the b.n = 'b' condition is guaranteed to fail > when b.* is nulled out ...
You can make it work by moving parts of the condition into the explicit join clause: select a.i from t as a left join t as b on a.n='a' and b.n='b' and a.i=b.i where a.n='a' and b.i is null; (notice you still need the check on a.n='a' outside the join condition) -- Andrew, Supernews http://www.supernews.com - individual and corporate NNTP services ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
