Re: Odd error when using UNION and COLLATE

On Wed, Jul 20, 2016 at 5:38 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> I think the 'ORDER BY x COLLATE "C"' is being parsed as an a_expr, and
> we don't allow a_expr in a UNION. Perhaps we are too strict here, but I
> can't tell.
>

​ORDER BY 1 COLLATE "C" is indeed an expression - the number no longer
refers to a column position but it is a constant. The presence or absence
of UNION doesn't factor into things here - the expression itself is useless
on its face.​

This one is a bit different in cause but I suspect is working as well as
can be expected.

SELECT 'a-c' AS x UNION ALL SELECT 'ab' AS x ORDER BY x COLLATE "C";

​David J.​