Bryn Llewellyn <bryn@xxxxxxxxxxxx> 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
