| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bryn Llewellyn <bryn(at)yugabyte(dot)com> |
| Cc: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>, pgsql-general list <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Re: Where's the doc for "array()" — as in "select array(values (17), (42))" |
| Date: | 2022-09-19 17:05:16 |
| Message-ID: | 456815.1663607116@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Bryn Llewellyn <bryn(at)yugabyte(dot)com> writes:
> This works fine:
> select length( (select 'dog') )
> But without the doubled parentheses, it causes a syntax error.
The parens are required for it to be a valid scalar subquery, as per
https://www.postgresql.org/docs/current/sql-expressions.html#SQL-SYNTAX-SCALAR-SUBQUERIES
The reason ARRAY() is different is exactly that its argument is
directly a subquery, not an expression that chances to be a
scalar subquery.
> On the other hand, an extra pair of surrounding parentheses here
> select array( (values (17), (42)) )
> while not necessary, *is* tolerated.
You can pretty much always add *extra* parens in any expression
context.
regards, tom lane
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