【MySQL】查询重复记录以及从另一个表更新数据

记录两条SQL语句，免得忘了

第一条：查找单表重复记录

SELECT * FROM table_name WHERE column IN (SELECT column FROM table_name GROUP BY column HAVING COUNT(column)>1)

实例：

SELECT * FROM `stu_info` WHERE telenum IN (SELECT telenum FROM stu_info GROUP BY telenum HAVING COUNT(telenum)>1)

第二条：根据一个表的某个字段更新另一个表的某个字段

UPDATE table1 SET column = (SELECT table2.date FROM table2 WHERE table1.column = table2.column)

实例：

UPDATE `stu_info` SET date = (SELECT all_info.date FROM all_info WHERE stu_info.telenum = all_info.telenum)

以上语句很简单，均为语句嵌套，可以自行理解