2023.9.3
排序查询SQL语句笔记如下：
#查询员工信息，要求工资从高到低（从低到高）排序。
SELECT * FROM `employees` ORDER BY salary DESC;
SELECT * FROM `employees` ORDER BY salary ASC;#不写ASC默认升序
#查询部门编号>=90的员工信息，按入职时间的先后进行排序
SELECT * FROM `employees` WHERE department_id>=90 ORDER BY `hiredate` ASC;
#按年薪的高低显示员工的信息和年薪【按表达式排序】
SELECT *,salary*12*(1+IFNULL(`commission_pct`,0)) AS 年薪 FROM `employees` ORDER BY 年薪 DESC;
#按姓名的长度显示员工的姓名和工资【按函数排序】
SELECT LENGTH(last_name) AS 姓名长度, `last_name`,`salary` FROM `employees` ORDER BY LENGTH(`last_name`) ASC;
#查询员工信息，要求先按工资排序，再按员工编号排序【按多个字段排序】
SELECT * FROM `employees` ORDER BY salary ASC,`employee_id` ASC;课后习题：
1.
查询员工的姓名和部门号和年薪，按年薪降序 按姓名升序
2.
选择工资不在
8000
到
17000
的员工的姓名和工资，按工资降序
3.
查询邮箱中包含
e
的员工信息，并先按邮箱的字节数降序，再按部门号升序
#排序查询测试题
SELECT `last_name`,`department_id`,salary*12*(1+IFNULL(`commission_pct`,0)) AS 年薪 FROM `employees` ORDER BY 年薪 DESC,LENGTH(`last_name`) ASC;
SELECT `last_name`,`salary` FROM `employees` WHERE `salary`<8000 OR `salary`>17000 ORDER BY `salary` DESC;
SELECT * FROM `employees` WHERE `email` LIKE '%e%' ORDER BY LENGTH(`email`) DESC,`department_id` ASC;