MySQL、Oracle中group by的用法区别

表结构：

表数据：

MySQL中group by的使用

1.select中包含的是group by的列

SELECT sex FROM student group by sex;

2.select中可以包含非group by的列

SELECT sex,age FROM student group by sex;

3.group by包含多个列

SELECT * FROM student group by sex,age;

Oracle中group by的使用

数据与上面的相同

1.select中包含的是group by的列

SELECT "sex" from "student" GROUP BY "sex" ;

2.select不能包含非group by 的字段（聚合函数除外）

SELECT "sex","age" FROM "student" group by "sex";

注意：Oracle中select不能包含非group by的列，但是可以包含非group by的列的聚合函数

3.select可以包含非group by的列的聚合函数

SELECT "sex",sum("age") FROM "student" group by "sex";

4.group by包含多个列

SELECT * FROM "student" group by "sex","age";

SELECT "sex","age" FROM "student" group by "sex","age";

SELECT "sex","age",count(*) FROM "student" group by "sex","age";