Question

我正在使用SQL Server 2012并且我有以下T-SQL查询：

SELECT a.ResaID,
       b.CheckInDate, 
       c.ProfileID  

FROM RSD a
LEFT JOIN GSS b on b.ResaID = a.ResaID
LEFT JOIN RS c on c.ResaID = a.ResaID
LEFT JOIN Profile d on d.ProfileID = c.ProfileID

上述查询输出的摘录如下所示：

  ResaID      CheckInDate    ProfileID

  100         2018-03-10      450
  101         2018-03-15      658
  102         2018-03-15      658
  103         2018-03-24      700
  115         2018-06-11      700
  127         2018-07-09      851

我需要过滤此输出，以便它仅根据ProfileID向我提供CheckInDate唯一的记录。换句话说，具有相同ProfileID和相同CheckInDate的记录应仅出现一次（仅表示具有第一个ResaID的记录）。具有相同ProfileID但具有不同CheckInDate的记录应完整显示（即，如果有2条记录，则输出将包括两条记录）。

根据上面给出的提取输出，所需的输出如下：

ResaID      CheckInDate    ProfileID

  100         2018-03-10      450
  101         2018-03-15      658
  103         2018-03-24      700
  115         2018-06-11      700
  127         2018-07-09      851

我怎样才能做到这一点？

Answer 1

尝试这样的事情

SELECT MIN(a.ResaID) AS FirstResaID,
       b.CheckInDate, 
       c.ProfileID  

FROM RSD a
LEFT JOIN GSS b on b.ResaID = a.ResaID
LEFT JOIN RS c on c.ResaID = a.ResaID
LEFT JOIN Profile d on d.ProfileID = c.ProfileID
GROUP BY c.ProfileID,b.CheckInDate;

我使用MIN()来获取第一个 ResaID - 假设这是IDENTITY ID，较小的值是第一个一个。如果这是错误的，您需要sorting规则来定义第一个。

Answer 2

我认为你需要一个简单的GROUP BY

SELECT min(a.ResaID) ResaID, 
       b.CheckInDate, 
       c.ProfileID  

FROM RSD a
LEFT JOIN GSS b on b.ResaID = a.ResaID
LEFT JOIN RS c on c.ResaID = a.ResaID
LEFT JOIN Profile d on d.ProfileID = c.ProfileID
group by
       b.CheckInDate, 
       c.ProfileID

Answer 3

您不使用个人资料表你确定你需要离开吗？

SELECT min(a.ResaID),
       b.CheckInDate, 
       c.ProfileID  
FROM RSD a
JOIN GSS b on b.ResaID = a.ResaID
JOIN RS c  on c.ResaID = a.ResaID 
group by b.CheckInDate, c.ProfileID

简化版

DECLARE @T1 TABLE (id int primary key);
DECLARE @T2 TABLE (id int primary key, fk int);

INSERT INTO @T1
VALUES (1), (2), (3), (4);

INSERT INTO @T2
VALUES (1, 1), (2, 1), (3, 2), (4, 2);

SELECT t1.id as [t1.id], t2.id as [t2.id], t2.fk as [t2.fk]
FROM @T1 T1
LEFT JOIN @T2 T2 
  ON t1.ID = t2.fk;

SELECT min(t1.ID) as minT1, t2.fk
FROM @T1 T1
LEFT JOIN @T2 T2 
  ON t1.ID = t2.fk
GROUP BY t2.fk;

SELECT min(t1.ID) as minT1, t2.fk
FROM @T1 T1
JOIN @T2 T2 
  ON t1.ID = t2.fk
GROUP BY t2.fk;

如何根据此特定条件过滤我的记录？

3 个答案: