Re: ORDER BY col is NULL in UNION causes error?

Alvaro Herrera wrote:
> Bruce Momjian wrote:
>
> > Here the column result is an expression, and you reference that.
> > Updated wording:
> >
> >  test=> select * from test union select * from test order by x is null;
> >  ERROR:  A UNION/INTERSECT/EXCEPT ORDER BY cannot use expressions or functions, only result column names
>
> This seems at odds with our message style guidelines.  I'd suggest
> putting the actual error message in errmsg() and the rest as a errhint,
> maybe
>
> (errmsg("invalid UNION/INTERSECT/EXCEPT ORDER BY clause"),
>  errhint("You may specify only output result column names in the ORDER BY clauses."))
>
> or something like that.

Updated wording:

 test=> SELECT * FROM test UNION SELECT * FROM test ORDER BY X IS NULL;
 ERROR:  invalid UNION/INTERSECT/EXCEPT ORDER BY clause
 DETAIL:  Only result column names can be used, not expressions or functions.
 HINT:  Add the expression/function to every SELECT, or move the UNION into a FROM clause.

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  Bruce Momjian   bruce@momjian.us
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