Bryn Llewellyn <bryn@yugabyte.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
