标签:完全 nbsp inf drop info HERE 别名 问题 很多
数据完全一致的情况:
#MySQL不支持INTO
Create table temp (Select DISTINCT * from student);
DROP TABLE student;
Create table student (Select * from temp);
DROP TABLE temp;
#其他数据库
SELECT DISTINCT * INTO temp FROM student;
DROP TABLE student;
SELECT * INTO student FROM temp;
DROP TABLE temp;
个别字段一致:
DELETE FROM student WHERE id in (SELECT id FROM (SELECT id FROM student where id not in(SELECT MIN(id) id from student GROUP BY `name`)) as s1);
解析:
因为MySQL不能对同一个表,查询的同时进行更新,所以很多同学都会觉得这个问题比较简单。
SELECT id FROM student where id not in(SELECT MIN(id) id from student GROUP BY `name`);
上面的sql是先查询出所有有效数据,然后通过not in() 的方式找出需要删除的id,最后对结果进行一次包装,起一个别名,然后就可以正常删除了。
标签:完全 nbsp inf drop info HERE 别名 问题 很多
原文地址:https://www.cnblogs.com/tjpblog/p/11679439.html