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排序查询
order by [asc(升序,默认的)|desc(降序)]
order by 支持单个字段,多个字段,表达式,函数,别名
放在sql语句的最后面(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 的长度排序(要使用到一个函数Length())
SELECT * FROM employees ORDER BY LENGTH(last_name) DESC;
# 查询员工信息,先按工资排序,在按员工编号排序;
# (其实就是工资相等排不了,在按员工编号排序)
SELECT * FROM employees ORDER BY salary DESC,employee_id DESC;