SQL having 子句

HAVING 子句

在 SQL 中增加 HAVING 子句原因是，WHERE 关键字无法与聚合函数一起使用。

HAVING 子句可以让我们筛选分组后的各组数据。

SQL HAVING 语法

SQL HAVING 语法

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING aggregate_function(column_name) operator value;

 

练习地址：http://sqlfiddle.com/#!9/ad7c8b/12

 创建表插入数据

Create table If Not Exists Courses (student varchar(255), class varchar(255));
Truncate table Courses;
insert into Courses (student, class) values ('A', 'Math');
insert into Courses (student, class) values ('B', 'English');
insert into Courses (student, class) values ('C', 'Math');
insert into Courses (student, class) values ('D', 'Biology');
insert into Courses (student, class) values ('E', 'Math');
insert into Courses (student, class) values ('F', 'Computer');
insert into Courses (student, class) values ('G', 'Math');
insert into Courses (student, class) values ('H', 'Math');
insert into Courses (student, class) values ('I', 'Math');

执行练习

select class, count(student) as student
from courses
group by class
having count(student) >= 5
;