MySQL连接查询之非等值连接

非等值连接

等值连接中的等号改成非等号情况

创建一张job_grades工资级别表

create table job_grades(grade_level varchar(3),lowest_sal int,highest_sal int) ;
insert into job_grades values('A' , 1000,2999);
insert into job_grades values('B' , 3000,5999);
insert into job_grades values('C' , 6000,9999);
insert into job_grades values('D' , 10000,14999);
insert into job_grades values('E' , 15000,24999);
insert into job_grades values('F' , 25000,40000);

案例：查询员工的工资和工资级别

SELECT
salary,grade_level
FROM
employees e,job_grades jg
WHERE
salary BETWEEN jg.lowest_sal AND jg.`highest_sal`;
(非等值连接)