Allow parenthesized query expression for standard-compliance
------------------------------------------------------------
Key: CORE-6511
URL: http://tracker.firebirdsql.org/browse/CORE-6511
Project: Firebird Core
Issue Type: Improvement
Components: Engine
Reporter: Mark Rotteveel
Attachments: query-expr-v3.diff
See also discussion with subject "Standard-compliance for query expressions" on
firebird-devel (March 6th, 2021).
The SQL standard allows parentheses around query expressions (without
with-clause), and Firebird does not. It would be helpful if Firebird added this
support.
Specifically, SQL:2016 specifies the following:
```
<query expression> ::=
[ <with clause> ] <query expression body>
[ <order by clause> ] [ <result offset clause> ] [ <fetch first clause> ]
<query expression body> ::=
<query term>
| <query expression body> UNION [ ALL | DISTINCT ]
[ <corresponding spec> ] <query term>
| <query expression body> EXCEPT [ ALL | DISTINCT ]
[ <corresponding spec> ] <query term>
<query term> ::=
<query primary>
| <query term> INTERSECT [ ALL | DISTINCT ]
[ <corresponding spec> ] <query primary>
<query primary> ::=
<simple table>
| <left paren> <query expression body>
[ <order by clause> ] [ <result offset clause> ] [ <fetch first clause> ]
<right paren>
<simple table> ::=
<query specification>
| <table value constructor>
| <explicit table>
<query specification> ::=
SELECT [ <set quantifier> ] <select list> <table expression>
<table expression> ::=
<from clause>
[ <where clause> ]
[ <group by clause> ]
[ <having clause> ]
[ <window clause> ]
```
If I follow the grammar in parse.y correctly, the problem is that in Firebird,
<query primary> is basically <query specification>, so it's missing the
following alternative:
```
<left paren> <query expression body>
[ <order by clause> ] [ <result offset clause> ] [ <fetch first clause> ]
<right paren>
```
Adriano wrote the attached patch.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://tracker.firebirdsql.org/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
Firebird-Devel mailing list, web interface at
https://lists.sourceforge.net/lists/listinfo/firebird-devel
