Re: BUG #18594: CASE WHEN ELSE failing to return the expected output when the same colum is used in WHEN and ELSE

Hello Tom,
Thanks for the explanation and the link to the documentation. I understand
now what happened.
So it was a mistake on my side.
Thanks again for the patience and replies.

Best regards,

Francisco

El mié, 28 ago 2024 a las 20:11, Tom Lane (<tgl(at)sss(dot)pgh(dot)pa(dot)us>) escribió:

> =?UTF-8?Q?Francisco_J=2E_Ossand=C3=B3n?= <fco(dot)j(dot)ossandon(at)gmail(dot)com>
> writes:
> > So is the ELSE column hijacking the data type of the whole expression?
>
> It's the only CASE result that is supplying a definite type at all.
> But see
>
> https://www.postgresql.org/docs/current/typeconv-union-case.html
>
> particularly the footnote to the bit about "Select the first
> non-unknown input type as the candidate type, then consider
> each other non-unknown input type, left to right."
>
> The WHEN clauses have exactly nothing to do with the result type
> of the CASE: it's the THEN and ELSE clauses that supply the result.
>
> regards, tom lane
>

--
Francisco J. Ossandon
Bioinformatician
Ph.D. in Biotechnology