首先我的数剧是这样的：
我想根据name1、relation和name2判断如果重复的话删除重复的数据且保留id最小的一条数据，于是写了下面的sql语句
DELETE FROM star_relation WHERE (name1,relation,name2)IN (SELECT name1, relation, name2 FROM star_relation GROUP BY name1,relation,name2 HAVING COUNT( * ) > 1) AND id NOT IN (SELECT MIN(id) AS id FROM star_relation GROUP BY name1,relation,name2 HAVING COUNT( * ) > 1)
结果报了以下错误:[Err] 1093 - You can‘t specify target table ‘star_relation‘ for update in FROM clause
查找资料得知：大概是因为不能直接在查询的语句中进行操作。所以解决办法就是:将查询包装一层，于是有了下面的代码：（亲测有效）
DELETE FROM star_relation WHERE (name1,relation,name2)IN(SELECT name1, relation, name2 FROM (SELECT name1, relation, name2 FROM star_relation GROUP BY name1,relation,name2 HAVING COUNT( * ) > 1) a) AND id NOT IN (SELECT id FROM (SELECT MIN(id) AS id FROM star_relation GROUP BY name1,relation,name2 HAVING COUNT( * ) > 1)b)
原文：https://www.cnblogs.com/qianmo123/p/14639485.html