需要帮助找到正确的 T-SQL 查询

Question

我不太确定该怎么做。基本上我有一个像这样的表

UserId       DateRequested           Approved ApprovedBy  Notes
------------ ----------------------- -------- ----------- -----
1            2011-05-26               0        NULL        NULL
1            2011-05-27               0        NULL        NULL
1            2011-05-28               0        NULL        NULL
1            2011-06-05               0        NULL        NULL
1            2011-06-06               0        NULL        NULL
1            2011-06-25               0        NULL        NULL

，其中基本上包含员工请求休假的天数。现在，当授予一天或几天时，需要将这些数据复制到以下形式的表中

UserId DateFrom DateTo

，所以基本上对于我想要的上述数据：

UserId DateFrom DateTo 
-------------------------------
1      2011-05-26 2011-05-28 
1      2011-06-05 2011-06-06 
1      2011-06-25 2011-06-25 

即我想要 DateFrom 和 DateTo 中的连续天。现在我不知道如何在不使用 while 循环的情况下做到这一点。这是 SQL，所以我更喜欢非迭代解决方案。

请指教！！！

Answer 1

;WITH cte AS
(
SELECT *,
        DATEDIFF(DAY,0,DateRequested)-
        ROW_NUMBER() OVER (PARTITION BY UserId ORDER BY DateRequested) AS Grp
FROM YourTable  
WHERE Approved = 1 /*Presumably - but your example data doesn't show this.*/
)
SELECT UserId, 
       MIN(DateRequested) AS DateFrom, 
       MAX(DateRequested) AS DateTo  
FROM cte 
GROUP BY UserId,Grp

Answer 2

在 Oracle PL/SQL 中，它会写成如下：

WITH cte
        AS (SELECT a.*,
                   daterequested - TRUNC (SYSDATE)
                   - ROW_NUMBER ()
                        OVER (PARTITION BY UserId ORDER BY DateRequested)
                      AS Grp
              FROM yourtable a
             WHERE Approved = 0)
  SELECT UserId, MIN (DateRequested) AS DateFrom, MAX (DateRequested) AS DateTo
    FROM cte
GROUP BY UserId, Grp;