如何查找连续的行，员工是否缺席＆＃39;？

Question

我有一个表名雇员。它有4列：id，name，statuse和date_present。

date_present列包含员工在场和缺席的所有日期。我需要写一个查询来查找是否有员工连续缺席超过3天。

id | name | statuse | date_presnet
1  | khan | present | 2016-12-1
2  | jan  | present | 2016-12-2
3  | Kiran| absent  | 2016-12-3
4  | jan  | absent  | 2016-12-4
4  | jan  | absent  | 2016-12-5
4  | jan  | absent  | 2016-12-6

Answer 1

MySQL（或实际上在任何数据库中）的一种方法是使用join将记录连接到下一个日期：

select t.*
from t join
     t t2
     on t2.id = t1.id and
        t2.date = date_add(t1.date, interval 1 day) and
        t2.status = 'absent' and t.status = 'absent' join
     t t3
     on t3.id = t1.id and
        t3.date = date_add(t1.date, interval 2 day) and
        t3.status = 'absent' ;