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1 | 1 | <!-- |
2 | | -$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.35 2000/12/12 05:07:59 tgl Exp $ |
| 2 | +$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.36 2001/01/08 21:30:37 tgl Exp $ |
3 | 3 | Postgres documentation |
4 | 4 | --> |
5 | 5 |
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@@ -616,7 +616,12 @@ SELECT title, date_prod + 1 AS newlen FROM films ORDER BY newlen; |
616 | 616 | <programlisting> |
617 | 617 | SELECT name FROM distributors ORDER BY code; |
618 | 618 | </programlisting> |
619 | | - |
| 619 | + A limitation of this feature is that an ORDER BY clause applying to the |
| 620 | + result of a UNION, INTERSECT, or EXCEPT query may only specify an output |
| 621 | + column name or number, not an expression. |
| 622 | + </para> |
| 623 | + |
| 624 | + <para> |
620 | 625 | Note that if an ORDER BY item is a simple name that matches both |
621 | 626 | a result column name and an input column name, ORDER BY will interpret |
622 | 627 | it as the result column name. This is the opposite of the choice that |
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