DROP TABLE IF EXISTS aaa;
CREATE TABLE aaa (id bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',akey bigint(20) NOT NULL,avalue bigint(20) NOT NULL,time timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '记录日期',
PRIMARY KEY(id)
)ENGINE=InnoDB CHARSET=utf8;
INSERT INTO aaa(akey,avalue,time)VALUES
(1,2,'2010-10-09 15:58:20'),
(1,2,'2010-10-09 15:58:21'),
(1,2,'2010-10-09 15:58:22'),
(2,2,'2010-10-09 15:58:20'),
(2,2,'2010-10-09 15:58:21'),
(2,1,'2010-10-09 15:58:28');
我想根据akey和avalue两个条件进行判断查询，只要满足他们两个值都相等记录的最新一条就行，
例如
(1,2,'2010-10-09 15:58:20'),
(1,2,'2010-10-09 15:58:21'),
(1,2,'2010-10-09 15:58:22'),
这三条记录都一样的，key与value都相等，我要取最新一条记录，也就是最后一条，mysql语句怎么写？
[quote]我要过滤掉所有的重复记录，没有重复记录的也要查询出来。[/quote]
什么意思 上面的就没有重复记录的了啊
mysql> select akey, avalue, max(time) from aaa where akey='1' and avalue='2';
+------+--------+---------------------+
| akey | avalue | max(time) |
+------+--------+---------------------+
| 1 | 2 | 2010-10-09 15:58:22 |
+------+--------+---------------------+
1 row in set (0.00 sec)
mysql> select akey,avalue,max(time) from aaa group by concat(akey,avalue);
+------+--------+---------------------+
| akey | avalue | max(time) |
+------+--------+---------------------+
| 1 | 2 | 2010-10-09 15:58:22 |
| 2 | 1 | 2010-10-09 15:58:28 |
| 2 | 2 | 2010-10-09 15:58:21 |
+------+--------+---------------------+
3 rows in set (0.00 sec)