SQL 每日一题（6）
继续做题！
原始表：employee_resignations表
employee_id | resignation_date |
|---|---|
| 1001 | 2022-03-15 |
| 1002 | 2022-11-20 |
| 1003 | 2023-01-05 |
| 1004 | 2023-07-12 |
| 1005 | 2024-02-28 |
第一题：
查询累计到每个年度的离职人数
结果输出：年度、当年离职人数、累计离职人数
第二题：
第一次累计超过 100 人离职的是哪一年？对应的当年离职人数为多少？
填写示例：2008 120
第一题思路：累积离职利用sum窗口函数求和即可，当年离职利用order by排序即可
SELECTYEAR(resignation_date) AS year,COUNT(*) AS current_year_resignations,SUM(COUNT(*)) OVER (ORDER BY YEAR(resignation_date)) AS cumulative_resignations
FROM employee_resignations
GROUP BY YEAR(resignation_date)
ORDER BY YEAR(resignation_date);第二题思路，将第一题转换为t1表，在t1表基础上进行查询即可
WITH t1 AS (SELECT YEAR(resignation_date) AS year,COUNT(*) AS current_year_resignations,SUM(COUNT(*)) OVER (ORDER BY YEAR(resignation_date)) AS cumulative_resignationsFROM employee_resignationsGROUP BY YEAR(resignation_date)
)
SELECT year,current_year_resignations
FROM t1
WHERE cumulative_resignations >= 100
ORDER BY cumulative_resignations DESC
LIMIT 1;