mysql - 删除所有值并留下一个

Question

我有一个像这样的表:

uid | name | user_id
--------------------
1   | aaa  | 111 
2   | bbb  | 111
3   | ccc  | 222
4   | aaa  | 222
5   | vvv  | 333
6   | zzz  | 333
7   | aaa  | 111
8   | bbb  | 111

我想编写一个查询，它会删除所有名称aaa，但留下一次aaa。

输出如下:

  uid | name | user_id
  --------------------
    1 | aaa  | 111
    2 | bbb  | 111
    3 | ccc  | 222
    4 | aaa  | 222
    5 | vvv  | 333
    6 | zzz  | 333

可以通过查询吗？

Answer 1

DELETE  a
FROM    table tbl
        LEFT JOIN
        (
            SELECT  user_id, MIN(uid) min_uid, name
            FROM    table
            GROUP   BY user_id, name
        ) tbl1 ON  tbl.user_id = tbl1.user_id AND
                tbl.uid = tbl1.min_uid AND
                tbl.name = tbl1.name
WHERE   tbl1.user_id IS NULL

您必须比较名称和 uid 才能删除所有重复值。