值的连续出现

Question

我必须按学生缺勤日期计算连续次。

在两个类别中：2 次连续 fouls/absences 和 3 次或更多次连续犯规。

数据示例：

Name	Date	Present
Student 1	2022/01/01	false
Student 1	2022/01/02	false
Student 1	2022/01/03	true
Student 1	2022/01/04	false
Student 1	2022/01/05	false
Student 1	2022/01/06	false
Student 1	2022/01/07	true
Student 1	2022/01/08	false
Student 1	2022/01/09	false
Student 1	2022/01/10	false
Student 1	2022/01/11	false
Student 1	2022/01/12	true
Student 1	2022/01/13	false
Student 1	2022/01/14	false
Student 1	2022/01/15	true

预期结果：

Students	Count 2 Consecutive Absences	Count 3 consecutives or more	Total of Absences
Student 1	2	2	11

我尝试使用 LAG 和 OVER 执行此代码，但没有成功。

CASE WHEN LAG(present) OVER (order by date) is false AND present is false THEN 1 END as test

Answer 1

考虑以下方法

select name, 
  countif(absences = 2) as Count_2_Consecutive_Absences,
  countif(absences > 2) as Count_3_or_more_Consecutive_Absences,
  sum(absences) as Total_Absences,
from (
  select name, countif(not present) absences
  from (
    select *, countif(new_grp) over(partition by name order by date) grp
    from (
      select *, ifnull(present != lag(present) over(partition by name order by date), true) new_grp
      from your_table
    )
  )
  group by name, grp
  having absences > 0
)
group by name

如果应用于您问题中的示例数据 - 输出为

Answer 2

这是一个间隙和孤岛问题，一旦方法使用行数差异方法：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Date) rn1,
              ROW_NUMBER() OVER (PARTITION BY Name, Present ORDER BY Date) rn2
    FROM yourTable
),
cte2 AS (
    SELECT Name,
           COUNT(CASE WHEN Present = false THEN 1 END) AS num_consec_absent
    FROM cte
    GROUP BY Name, rn1 - rn2
)

SELECT Name,
       COUNT(CASE WHEN num_consec_absent = 2
                  THEN 1 END) AS Count_2_Consecutive_Absences,
       COUNT(CASE WHEN num_consec_absent > 2
                  THEN 1 END) AS Count_3_or_more_Consecutive_Absences,
       SUM(num_consec_absent) AS Total_Absences
FROM cte2
GROUP BY Name;

这是 SQL 服务器的运行 demo。

值的连续出现

Consecutive Occurrences of Values

google-bigquery