排序查詢

order by [asc(升序，預設的)|desc（降序）]

order by 支援單個欄位，多個欄位，表示式，函式，別名

放在sql語句的最後面（limit 子句 除外）；

SELECT * FROM employees ORDER BY salary;
SELECT * FROM employees ORDER BY salary DESC;
SELECT * FROM employees WHERE department_id >=90 ORDER BY hiredate DESC;

# 按年薪排序
SELECT * ,salary*12*(1+IFNULL(commission_pct,0)) nx 
FROM employees
ORDER BY nx DESC;

# 更last_name 的長度排序(要使用到一個函式Length（）)
SELECT * FROM employees ORDER BY LENGTH(last_name) DESC;

# 查詢員工資訊，先按工資排序，在按員工編號排序；
# (其實就是工資相等排不了，在按員工編號排序)
SELECT * FROM employees ORDER BY salary DESC,employee_id DESC;