t-sql 从平面日期列表中汇总日期范围，按其他列分组

Question

Suppose I had the following table:

UserId   AttributeId   DateStart
1        3             1/1/2020
1        4             1/9/2020
1        3             2/2/2020
2        3             3/5/2020
2        3             4/1/2020
2        3             5/1/2020

For each unique UserId/AttributeId pair, it is assumed that the DateEnd is the day prior to the next DateStart for that pair, otherwise it is null (or some default like crazy far into the future - 12/31/3000).

Applying this operation to the above table would yield:

UserId   AttributeId   DateStart     DateEnd
1        3             1/1/2020      2/1/2020
1        4             1/9/2020      <null>
1        3             2/2/2020      <null>
2        3             3/5/2020      3/31/2020
2        3             4/1/2020      4/30/2020
2        3             5/1/2020      <null>

What T-SQL, executing in SQL Server 2008 R2, would accomplish this?

Answer 1

I have changed query)

Try this please:

  SELECT 
  UserId,AttributeId,DateStart,Min(DateEnd)DateEnd
  FROM
  (
 
   SELECT X.UserId,X.AttributeId,X.DateStart, DATEADD(DD,-1,Y.DateStart) DateEnd
   FROM TAB X LEFT JOIN TAB Y
   ON (X.UserId=Y.UserId) AND (X.AttributeId=Y.AttributeId)
   AND   (X.DateStart<Y.DateStart) 

  )
 T
 GROUP BY UserId,AttributeId,DateStart
 ORDER BY DateStart

Answer 2

You are describing lead() :

select t.*,
       dateadd(day, -1, lead(dateStart) over (partition by userId, attributeId order by dateStart)) as dateEnd
from t;