🔴 185. 部门工资前三高的员工

Employee 表包含所有员工信息，每个员工有其对应的 Id, salary 和 department Id 。

Department 表包含公司所有部门的信息。

编写一个 SQL 查询，找出每个部门工资前三高的员工。例如，根据上述给定的表格，查询结果应返回：

解答:

SELECT
    Department,
    Employee,
    Salary 
FROM
    (
    SELECT Department,Employee,Salary,
        @rowNum :=IF(@LastD = t.Department,@rowNum + ( @lastS <> t.Salary ),1 ) AS seq,
        @lastD := t.Department,
        @lastS := t.Salary 
    FROM
        (SELECT d.NAME Department,e.NAME Employee,Salary 
         FROM Employee e,Department d 
         WHERE e.DepartmentId = d.Id 
         ORDER BY d.NAME,Salary DESC ) t,
        (SELECT @lastD:= -1,@lastS:= -1,@rowNum:= 0 ) AS init 
    ) AS t2 
WHERE t2.seq <= 3;