"Tom Lane" <[EMAIL PROTECTED]> writes: > Gregory Stark <[EMAIL PROTECTED]> writes: > >> Does it even matter except in the case of nulls? I mean, if the inner pair >> uses integer and then the outer pair uses bigint it'll still work correctly, >> no? > > Oh, it absolutely matters: you can get different answers. Consider > > (select '1' union select ' 1') union all select 1;
Ah. >> What would happen if the inner pair defaulted null to "unknown" instead of >> text? > > You're missing the point, which is that the inner UNION needs to decide > what its uniqueness semantics are, independently of what might happen to > its result later. Or that's how I read the spec anyway. Ah of course. We wouldn't be able to unionize "unknown" all. hmph. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
