"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;


>> 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

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