Question

我有三张桌子

建筑物

BuildingKey(int) | BuildingID(varchar) | ...

领域

areaKey(int) | areaID(varchar) | buildingKey(int-FK[Buildings]) | ...

交易

transactionKey(int) | areaKey(int-FK[Areas]) | value(float) | trnDateTime(DateTime)

Areas中可能有多个Building。

所有区域都有许多Transactions，不同value和trnDateTime不同。

我想要做的是获取value的每个 Area的最新Building（交易）（当buildingKey是DECLARE @buildingKey INT SET @buildingKey = 3 ;WITH Vals AS ( SELECT T.areaKey AS AreaKey, T.value AS CurrentValue, T.trnDateTime AS RecordedDateTime, ROW_NUMBER() OVER (PARTITION BY B.buildingKey ORDER BY T.trnDateTime DESC) RowID FROM Buildings B INNER JOIN Areas A ON B.buildingKey = A.buildingKey INNER JOIN Transactions T ON A.areaKey = T.areaKey WHERE B.buildingKey = @buildingKey ) SELECT AreaKey, CurrentValue, MAX(RecordedDateTime) AS RecentReading, RowID FROM Vals WHERE RowID = 1 GROUP BY AreaKey, CurrentValue, RowID时给出）。

我之前提到了this one之类的一些问题，并尝试了以下问题。

（1）

DECLARE @buildingKey INT
SET @buildingKey = 3

SELECT  A.areaKey AS AreaKey, 
        A.areaID AS AreaID,
        T.value AS CurrentValue,
        T.trnDateTime AS RecordedDateTime                   

FROM Areas A, Buildings B, Transactions T

WHERE   @buildingKey = B.buildingKey AND 
        B.buildingKey = A.buildingKey AND
        T.areaKey = A.areaKey AND
        T.trnDateTime IN (SELECT MAX(T.trnDateTime), T.areaKey
                                  FROM Transactions T
                                  GROUP BY T.areaKey)

！）返回最新值（在所有区域中）; 不每个区域的最新值！

（2）

Msg 116, Level 16, State 1, Line 16
Only one expression can be specified in the select list when the subquery is not introduced with EXISTS.

！）给出错误 - ＆gt;

{{1}}

Answer 1

这将为您提供每个建筑物的最新区域。

(PARTITION BY B.BuildingKey, a.areaKey ORDER BY T.TransactionDateTime DESC) RowID

Answer 2

SELECT  A.areaKey AS AreaKey, 
        A.areaID AS AreaID,
        T.value AS CurrentValue,
        T.trnDateTime AS RecordedDateTime                   
FROM Areas A JOIN Buildings B ON B.buildingKey = A.buildingKey 
             JOIN Transactions T ON T.areaKey = A.areaKey 
WHERE @buildingKey = B.buildingKey AND EXISTS (
                                       SELECT 1
                                       FROM Transactions T2
                                       WHERE T.areaKey = T2.areaKey
                                       GROUP BY T2.areaKey
                                       HAVING MAX(T2.trnDateTime) = T.trnDateTime
                                               )

Answer 3

尝试

DECLARE @buildingKey INT
SET @buildingKey = 3

SELECT  A.areaKey AS AreaKey, 
        A.areaID AS AreaID,
        T.value AS CurrentValue,
        T.trnDateTime AS RecordedDateTime

FROM Areas A, Buildings B, Transactions T

WHERE   @buildingKey = B.buildingKey AND 
        B.buildingKey = A.buildingKey AND
        T.areaKey = A.areaKey AND
        T.trnDateTime IN (SELECT MAX(T.trnDateTime)
                                  FROM Transactions T
                                  GROUP BY T.areaKey)

选择具有最新日期时间值的记录

3 个答案: