3 ms·

I think it's even simpler. Starting a subquey here doesn't make sense since there is no main query. So the parens gets dropped promoting this query to main. Sam

• jamii 6y ago
  ORDER BY actually happens last. jamie=# (select a, a+1 as c from nums) order by b,c; a | c ---+--- 3 | 4 0 | 1 1 | 2 2 | 3 (4 rows) It's a separate part of the grammar: <query primary> ::= <simple table> | <left paren> <query expression body> [ <order by clause> ] [ <result offset clause> ] [ <fetch first clause> ] <right paren> But, if "QE is a <query expression body> that is a <query term> that is a <query primary> that is a <simpletable> that is a <query specification>" then the <order by clause> may select columns from the <table expression> even though those don't really exist any more by the time the <order by clause> runs. It's tricky to implement.