Question

Why does Oracle think it’s missing a right parenthesis?

SELECT table2.name
    FROM (SELECT id, count (*) AS num
            FROM table1 GROUP BY id WHERE x = 1) 
    table1, table2, table3
    WHERE table2.temp_id = table3.temp_id AND
      table1.num > = s.num AND
      table2.id = table3.id;

Answer 1

In your inline view, your WHERE clause is after your GROUP BY. You would need to reverse that

SELECT id, count (*) AS num
        FROM table1 WHERE x = 1 GROUP BY id)