SQL 取重复数据中ID号最小的数据

数据库操作中尽量不要使用条件“IN”语句

CREATE TABLE `zhoz_mst` (
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY ,
`title` VARCHAR( 66 ) NOT NULL ,
`kana` VARCHAR( 66 ) ,
`zz` VARCHAR( 66 ) NOT NULL
) ENGINE = MYISAM ;

插入测试数据：
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'aaa', 'bbb', 'ccc');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'aaa', 'bbb2', '2');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'aaa', 'bbb', '3');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'aaa', 'bbb', '4');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'a', 'b', '5');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'a', NULL, '6');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'a', NULL, '7');
INSERT INTO `zhoz0428`.`zhoz_mst` (`id` ,`title` ,`kana` ,`zz` )VALUES (NULL , 'a', 'b', '8');

1 aaa bbb ccc
2 aaa bbb2 2
3 aaa bbb 3
4 aaa bbb 4
5 a b 5
6 a NULL 6
7 a NULL 7

删除保存最小ID：
select a.id, a.title, a.kana from zhoz_mst a
where (a.title,a.kana) in (select title,kana from zhoz_mst group by title,kana having count(*) > 1)
and id not in (select min(id) from zhoz_mst group by title,kana having count(*)>1)

取出两字段完全相同：
select a.id, a.title, a.kana from zhoz_mst a
where (a.title,a.kana) in (select title,kana from zhoz_mst group by title,kana having count(*) > 1)
----------------------
1 aaa bbb
3 aaa bbb
4 aaa bbb
5 a b
8 a b

取最大ID号

select * from prn a
where a.flowid in(select max(flowid) from prn where tm>'2009-7-1' group by stcd )

取最大ID号语句优化

select * from prn a (select max(flowid) flowid from prn where tm>'2010-1-28'group by stcd ) b
where a.flowid=b.flowid