Форум пользователей MySQL

mysql> select * from a;
+------+------+------+
| c1   | c2   | c3   |
+------+------+------+
|    1 |    1 |    1 |
|    1 |    1 |    2 |
|    1 |    2 |    1 |
+------+------+------+
3 rows in set (0.17 sec)

mysql> create temporary table b (c1 int, c2 int, c3 int);
Query OK, 0 rows affected (0.14 sec)

mysql> insert into b select c1,c2,min(c3) from a group by c1,c2 having count(*)>1;
Query OK, 1 row affected (0.09 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> delete a,b from a join b using(c1,c2,c3);
Query OK, 2 rows affected (0.03 sec)

mysql> select * from a;
+------+------+------+
| c1   | c2   | c3   |
+------+------+------+
|    1 |    1 |    2 |
|    1 |    2 |    1 |
+------+------+------+
2 rows in set (0.00 sec)

mysql> drop table b;
Query OK, 0 rows affected (0.19 sec)