MySQL根据业务场景归纳常用SQL语句

素材表数据：user[{"id":1,"name":"x"},{"id":2,"name":"x"},{"id":3,"name":"y"},{"id":4,"name":"y"},{"id":5,"name":"z"},{"id":6,"name":"x"}]

场景：查询出表中"name"重复的所有记录

SQL：

　　第一步--根据group by 分组查询，根据“name”分组查出表中记录：select * from user group by name;

　　第二步--根据分组查询的结果，筛选出其中分组记录数大于1的"name"：select name from user group by name having count(*)>1;

　　第三步--根据上一步，使用“in”来包住满足要求的“name”字段的值，并由此查询出最终的结果：select * from user where name in (select name from user group by name having count(*)>1);

讨论：in和exists以及连接查询和子查询的内容待之后讨论补充。。。。

转载于:https://www.cnblogs.com/dayuanzi/p/10657287.html