1、执行sql语句报上面的错误：
DELETE
FROM
db_student
WHERE
RowGuid IN ( SELECT RowGuid FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > )
AND ID NOT IN ( SELECT MAX( ID ) AS id FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > )
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
SELECT *
FROM
db_student
WHERE
RowGuid IN (
SELECT
aa.RowGuid
FROM
( SELECT RowGuid FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > ) aa
)
AND ID NOT IN (
SELECT
t.id
FROM
( SELECT MAX( ID ) as id FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > ) t
) DELETE
FROM
db_student
WHERE
RowGuid IN (
SELECT
aa.RowGuid
FROM
( SELECT RowGuid FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > ) aa
)
AND ID NOT IN (
SELECT
t.id
FROM
( SELECT MAX( ID ) as id FROM db_student WHERE age = GROUP BY RowGuid HAVING count( * ) > ) t
)
待续......