SQL中如何統計員工最大連續打卡天數

針對員工最大連續打卡天數等類似問題SQL求解，思路如下，

示例數據如下，

id	date	success
1	2020/4/2	1
1	2020/4/3	1
1	2020/4/4	1
1	2020/4/5	0
1	2020/4/6	1
1	2020/4/7	1
2	2020/4/2	1
2	2020/4/3	1

1）通過窗口函數對員工打卡數據進行排序

id	date	rn
1	2020/4/2	1
1	2020/4/3	2
1	2020/4/4	3
1	2020/4/6	4
1	2020/4/7	5
2	2020/4/2	1
2	2020/4/3	2

2）計算當前打卡日期與序號差值，我們可以看到如果是連續打卡，則label_date值是相同的

id	date	rn	label_date
1	2020/4/2	1	2020/4/1
1	2020/4/3	2	2020/4/1
1	2020/4/4	3	2020/4/1
1	2020/4/6	4	2020/4/2
1	2020/4/7	5	2020/4/2
2	2020/4/2	1	2020/4/1
2	2020/4/3	2	2020/4/1

 

3）對label_date進行計數，取計數結果count_day的最大值即爲最大連續打卡天數

id	label_date	count_day
1	2020/4/1	3
1	2020/4/2	2
2	2020/4/1	2

SQL代碼如下，

select
	c.id,max(count_day) as max_day
from
(
	select
		b.id,b.label_date,count(*) as count_day
	from
	(
		select
			a.id,a.date,date_sub(a.date, cast(rn as int)) as label_date
		from
		(
			select 
				id,date, 
				row_number() over(partition by id order by date) as rn
			from events where success=1
		)a
	)b
	group by b.id,b.label_date
)c
group by c.id;