HAVING語句通常與GROUP BY語句聯合使用，用來過濾由GROUP BY語句返回的記錄集。

HAVING語句的存在彌補了WHERE關鍵字不能與聚合函式聯合使用的不足。

CREATE TABLE `tp5_student` (

  `id` int(11) DEFAULT NULL,

  `no` int(11) DEFAULT NULL COMMENT '學號',

  `course` varchar(255) DEFAULT NULL COMMENT '課程',

  `score` int(11) DEFAULT NULL COMMENT '分數'

) ENGINE=InnoDB DEFAULT CHARSET=utf8

SELECT id,no, COUNT(course) as numcourse, AVG(score) as avgscore

FROM tp5_student

GROUP BY no

SELECT id,no, COUNT(course) as numcourse, AVG(score) as avgscore

FROM tp5_student

GROUP BY no HAVING  AVG(score)>=85

SELECT id,no, COUNT(course) as numcourse, AVG(score) as avgscore

FROM tp5_student

WHERE  id>3

GROUP BY no