mysql学习打卡4

进阶3：排序查询

/*
语法：
	select 查询列表
	from 表
	【where 筛选条件】
	order by 排序列表 【asc|desc】
特点	
	1.默认升序
	2.可以多个字段，表达式，函数，别名都可
	3.查询语句的最后面，limit子句前面
*/

#1.工资从高到低
SELECT * 
FROM employees 
ORDER BY salary ASC;
SELECT * 
FROM employees 
ORDER BY salary DESC;

#2.查询部门编号>=90 按照入职时间先后排序
SELECT * 
FROM employees
WHERE department_id>=90
ORDER BY hiredate ASC; 

#3.按照年薪高低显示员工信息和年薪 没有年薪这个字段 按照表达式排序
SELECT *,salary*12*(1+IFNULL(commission_pct,0)) AS 年薪
FROM employees
ORDER BY salary*12*(1+IFNULL(commission_pct,0)) DESC;

#4.按照别名排序
SELECT *,salary*12*(1+IFNULL(commission_pct,0)) AS 年薪
FROM employees
ORDER BY 年薪 DESC;

#5.按照姓名长度排序 按照函数排序
SELECT LENGTH(last_name) AS 名字长度,last_name,salary
FROM employees
ORDER BY LENGTH(last_name);

SELECT LENGTH(last_name) AS 名字长度,last_name,salary
FROM employees
ORDER BY 名字长度;

#6.先按工资s升序排序，再按编号降序排序，按多个字段排序
SELECT *
FROM employees
ORDER BY salary ASC,employee_id DESC;

# 练习1  按年薪升序姓名降序
SELECT last_name,department_id,salary*12*(1+IFNULL(commission_pct,0)) AS 年薪
FROM employees
ORDER BY 年薪 DESC,last_name ASC;

# 练习2 选择工资不在8000到17000的员工的姓名和工资，按照工资降序
SELECT last_name,salary
FROM employees
WHERE salary NOT BETWEEN 8000 AND 17000
ORDER BY salary DESC;

# 练习3 邮箱包含e的员工信息，邮箱字节数降序，部门编号升序
SELECT *
FROM employees
WHERE email LIKE '%e%'
ORDER BY LENGTH(email) DESC,department_id ASC;