LeetCode--579. 查询员工的累计薪水

建表

DROP TABLE IF EXISTS employee; CREATE TABLE employee ( Id INT, MONTH INT, Salary DECIMAL ); INSERT INTO employee VALUES(1, 1, 20); INSERT INTO employee VALUES(2, 1, 20); INSERT INTO employee VALUES(1, 2, 30); INSERT INTO employee VALUES(2, 2, 30); INSERT INTO employee VALUES(3, 2, 40); INSERT INTO employee VALUES(1, 3, 40); INSERT INTO employee VALUES(3, 3, 60); INSERT INTO employee VALUES(1, 4, 60); INSERT INTO employee VALUES(3, 4, 70);

解题思路

用开窗函数求薪水，对id分组然后根据月份降序排列，需要去掉最近一个月即去掉top1

注意题目要求是三个月的总额,所以要加 ROWS 2 PRECEDING，将当前行和它前面的两行划为一个窗口

SELECT t.id, t.`month`, t.salary FROM ( SELECT id, `month`, SUM(salary) over(PARTITION BY id ORDER BY `month` ROWS 2 PRECEDING) salary, -- 累加的总薪水 rank() over(PARTITION BY id ORDER BY `month` DESC) ranks -- 排名好去掉最近一个月 FROM employee ) t WHERE t.ranks > 1