mysql中去除重复项，保留一天

query result(14 records)
id
uid
gid
1
11
502
2
107
502
3
100
503
4
110
501
5
112
501
6
104
502
7
100
502
8
100
501
9
102
501
10
104
502
11
100
502
12
100
501
13
102
501
14
110
501
第七条与第十一条重复等
方法一
mysql> create temporary table tmp_wrap select * from users_groups group by uid having count(1) >= 1;
Query OK, 7 rows affected (0.11 sec)
Records: 7  Duplicates: 0  Warnings: 0
mysql> truncate table users_groups;
Query OK, 14 rows affected (0.03 sec)
mysql> insert into users_groups select * from tmp_wrap;
Query OK, 7 rows affected (0.03 sec)
Records: 7  Duplicates: 0  Warnings: 0
mysql> select * from users_groups;
query result(7 records)
id
uid
gid
1
11
502
2
107
502
3
100
503
4
110
501
5
112
501
6
104
502
9
102
501
mysql> drop table tmp_wrap;
Query OK, 0 rows affected (0.05 sec)
2、还有一个很精简的办法。
查找重复的，并且除掉最小的那个。
delete users_groups as a from users_groups as a,
(
select *,min(id) from users_groups group by uid having count(1) > 1
) as b
 where a.uid = b.uid and a.id > b.id;
(7 row(s)affected)
(0 ms taken)
 
query result(7 records)
id
uid
gid
1
11
502
2
107
502
3
100
503
4
110
501
5
112
501
6
104
502
9
102
501