查询每个class中recordTime最新的一条记录
也就是name为b,d,e的记录
附上建表语句,插入数据的语句。
CREATE TABLE `a1` ( `id` int(11) NOT NULL auto_increment, `class` varchar(11) default NULL, `name` varchar(11) default NULL, `recordTime` datetime default NULL, PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT;INSERT INTO `a1` VALUES (1111,'1','a','1999-12-30 10:00:00');INSERT INTO `a1` VALUES (2222,'1','b','1999-12-30 11:00:00');INSERT INTO `a1` VALUES (3333,'2','c','2000-12-30 10:00:00');INSERT INTO `a1` VALUES (4444,'2','d','2000-12-30 12:00:00');INSERT INTO `a1` VALUES (5555,'3','e',NULL);INSERT INTO `a1` VALUES (6666,'2','f',NULL);
WHERE a.`class`=`class` AND COALESCE(a.`recordTime`,0)<COALESCE(`recordTime`,0));
所以不是b、d、e吗?