MySQL中连表查询分为等值连接和非等值连接

1.等值连接:

二）非等值连接:

#案例：查询部门编号在10-90之间的员工的工资级别，并按级别进行分组
SELECT * FROM sal_grade;


SELECT COUNT(*) 个数,grade
FROM employees e
JOIN sal_grade g
ON e.`salary` BETWEEN g.`min_salary` AND g.`max_salary`
WHERE e.`department_id` BETWEEN 10 AND 90
GROUP BY g.grade;

本人新手,肯定有理解错误的地方,还请大家不吝赐教,多多给予批评指正!
万般感谢!!!