一、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】
一般ORDER BY语句放在查询语句的最后【LIMIT子句除外】
案例
案例1：查询员工信息，要求工资从高到低排序
SELECT * FROM employees ORDER BY salary DESC;
查询员工信息，要求工资从低到高排序
SELECT * FROM employees ORDER BY salary ASC;
案例2：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;
案例3：按年薪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)) 年薪 FROM employees ORDER BY 年薪
案例4：按姓名长度显示员工的姓名和工资【按函数排序】
SELECT LENGTH(last_name) 字节长度,last_name,salary FROM employees ORDER BY 字节长度 DESC;
案例5：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 DESC;
二、MySQL查询测试题
1. 查询没有奖金，且工资少于18000的salary, last_name
SELECT salary, last_name FROMemployees WHERE commission_pct IS NULL AND salary<18000;
2. 查询employees表中，job_id不为'IT'或工资为12000的员工信息
SELECT * FROM employees WHERE job_id<>'IT' OR salary=12000;
3. 查询部门departments表中涉及到了哪些位置编号
SELECT DISTINCT location_id FROM departments;
4. SELECT & FROM employees 和 SELECT * FROM employees WHERE commission_pct like '%%' and last_name like '%%' 结果是否一样?
答：若字段有null值结果则不一样
5. 查询员工的姓名和部门号和年薪，按年薪降序，按姓名升序
SELECT last_name, department_id, salary*12*(1+IFNULL(commission_pct,0)) 年薪 FROM employees ORDER BY 年薪 DESC, last_name ASC;
6. 选择工资不在8000到17000的员工姓名和工资，按工资降序
SELECT last_name, salary FROM employees WHERE salary NOT BETWEEN 8000 and 17000 ORDER BY salary DESC;
7. 查询邮箱中包含e的员工信息，并按邮箱的字节数降序，再按部门号升序
SELECT * FROM employees WHERE email LIKE '%e%' ORDER BY LENGTH(email) DESC, department_idASC;
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