1、执行sql语句报上面的错误：
1 DELETE 2 FROM 3 db_student 4 WHERE 5 RowGuid IN ( SELECT RowGuid FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 ) 6 AND ID NOT IN ( SELECT MAX( ID ) AS id FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 )
报错如下所示
You can't specify target table 'xxx' for update in FROM clause。
原因：因为在MYSQL里，不能先select一个表的记录，在按此条件进行更新和删除同一个表的记录。
详细参考：https://blog.csdn.net/h996666/article/details/81699255
1 SELECT * 2 FROM 3 db_student 4 WHERE 5 RowGuid IN ( 6 SELECT 7 aa.RowGuid 8 FROM 9 ( SELECT RowGuid FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 ) aa 10 ) 11 AND ID NOT IN ( 12 SELECT 13 t.id 14 FROM 15 ( SELECT MAX( ID ) as id FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 ) t 16 ) 17 18 19 DELETE 20 FROM 21 db_student 22 WHERE 23 RowGuid IN ( 24 SELECT 25 aa.RowGuid 26 FROM 27 ( SELECT RowGuid FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 ) aa 28 ) 29 AND ID NOT IN ( 30 SELECT 31 t.id 32 FROM 33 ( SELECT MAX( ID ) as id FROM db_student WHERE age = 22 GROUP BY RowGuid HAVING count( * ) > 1 ) t 34 )
待续......