HAVING

http://stackoverflow.com/questions/287474/whats-the-difference-between-having-and-where

HAVING is similar to WHERE, but:

• HAVING can refer to columns generated via AS or aggregate functions.

  CREATE TABLE t (c0 INT, c1 INT);
  INSERT INTO t VALUES (1, 1), (2, 4), (3, 9);
  SELECT c0+c1 AS sum FROM t HAVING sum > 3 ORDER BY sum;
  DROP TABLE t;
  

  Output:

  sum
  6
  12
  

• HAVING is applied after GROUP BY while WHERE is applied before.

  CREATE TABLE t (c0 CHAR(1), c1 INT);
  INSERT INTO t VALUES ('a', 1), ('a', 2), ('b', 3), ('b', 3);
  SELECT c0, SUM(c1) AS sum FROM t GROUP BY c0 HAVING sum > 4;
  DROP TABLE t;
  

  Output:

  c0   sum
  b    6