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 ;
人生还有意义。那一定是还在找存在的理由