Hi,
>I see. So this has to do with the union; after combining the two
>queries, the tables from the FROM clauses are no longer available.
this has nothing to do with the UNION, but with the fact that the result set is ordered after being produced, so you can order by any of its elements, and only by that. You can actually order by calling them acording to their position in the result set, like in:
SELECT
relname,
relpages
FROM pg_class
ORDER BY 1;
where 1 is actually the first element (no matter how it's called). The table as such is never available to ORDER BY, no matter how simple your query is.
Bèrto
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