Today, a bug in a development version of Hibernate 6.0 reminded me of
problem that Firebird has with query expressions, specifically with
parentheses around selects.
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>
```
Now I wonder, what would be necessary to introduce this alternative?
Would this be a matter of adding the right alternative and adding the
order by and offset/fetch info to the RseNode returned by the query
expression, or would more be needed?
Mark
--
Mark Rotteveel
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