mysql sql99语法 内连接非等值连接详解

#案例：查询员工的工资级别

SELECT
  salary,grade_level
FROM
  employees e
JOIN
  job_grades g
ON
  e.`salary` BETWEEN g.`lowest_sal` AND g.`lowest_sal`;

#案例：查询每个工资级别的个数，并且按级别降序

SELECT
  COUNT(*),grade_level
FROM
  job_grades j
JOIN
  employees e
ON
  e.`salary` BETWEEN j.`lowest_sal`AND j.`highest_sal`
GROUP BY
  grade_level DESC;

内容扩展：

语法

select 查询列表

from 表1 别名 [连接类型]

jion 表2 别名

on 连接条件

[where 筛选条件]

[group by 分组]

[having 筛选条件]

[order by 排序列表]

案例1:查询员工名,部门名

SELECT last_name,department_name
FROM employees e
INNER JOIN departments d
ON e.department_id=d.department_id;

案例2:查询名字中包含e的员工名和工种名(添加筛选)

SELECT last_name,job_title
FROM employees e
INNER JOIN jobs j
ON e.job_id=j.job_id
WHERE e.last_name LIKE ‘%e%';

以上就是本次介绍的全部知识点内容。