CREATE TABLE a
(id INT)
CREATE TABLE B
(cid INT
,createDate DATETIME)
INSERT INTO a
SELECT 1
UNION
SELECT 2
INSERT INTO b SELECT 1,'2016-02-19'
UNION SELECT 1,'2016-02-18'
UNION SELECT 2,'2016-02-17'
UNION SELECT 2,'2016-02-16'
UNION SELECT 2,'2016-02-15'
SELECT * FROM a
LEFT JOIN (SELECT MAX(createDate)AS createDate,cid FROM b GROUP BY cid) b1
ON b1.cid = a.id
文章来源于：https://blog.csdn.net/zhu_nana/article/details/50699551