僅更新標識的日期最新的SQL（6 2）

Question

我有以下表格：

和：

我制定此查詢：

Update Table 1 
SET DY_H_ID = ( 

    SELECT MAX(ID) 
    FROM Table 2 
    WHERE H_DateTime <= DY_Date 
    AND H_IDX = DY_IDX 
    AND H_HA_ID = 7 
    AND H_HSA_ID = 19 
    AND H_Description LIKE 'Diary item added for :%' 

) 
WHERE DY_H_ID IS NULL AND DY_IDX IS NOT NULL 

其中產品：

然而，這個查詢更新所有6行。我只需要更新最新日期的兩行，即'2013-08-29 15:00:00.000'。這意味着6條記錄中只有2條會被更新，其他4條會保持爲NULL。

如何通過添加上述查詢來做到這一點？我知道這可能不太理想，但沒有選擇，只能做這樣的事情。我不明白的是，你如何只選擇最新的日期而不對其進行硬編碼。這些數據可以改變，它不會永遠是同一日期等

Answer 1

試試這個：

UPDATE TABLE 1 
SET DY_H_ID = (SELECT Max(ID) 
        FROM TABLE 2 
        WHERE H_DATETIME <= DY_DATE 
         AND H_IDX = DY_IDX 
         AND H_HA_ID = 7 
         AND H_HSA_ID = 19 
         AND H_DESCRIPTION LIKE 'Diary item added for :%') 
WHERE DY_H_ID IS NULL 
     AND DY_IDX IS NOT NULL 
     AND DY_DATE = (SELECT Max(DY_DATE) 
         FROM TABLE1) 

Answer 2

只需添加另一個條件的地方：

Update Table 1 
SET DY_H_ID = ( 

    SELECT MAX(ID) 
    FROM Table 2 
    WHERE H_DateTime <= DY_Date 
    AND H_IDX = DY_IDX 
    AND H_HA_ID = 7 
    AND H_HSA_ID = 19 
    AND H_Description LIKE 'Diary item added for :%' 

) 
WHERE DY_H_ID IS NULL AND DY_IDX IS NOT NULL 
and DY_Date = (select max(DY_Date) from Table 1) 

Answer 3

使用CTE，與SQL-Server-2005兼容或更高版本

;WITH cte AS (
    SELECT H_IDX, MAX(ID) MaxID 
    FROM Table2 
    WHERE H_HA_ID = 7 
      AND H_HSA_ID = 19 
      AND H_Description LIKE 'Diary item added for :%' 
    GROUP BY H_IDX 
) 
Update Table1 
SET DY_H_ID = MaxID 
FROM Table1 
INNER JOIN CTE ON cte.H_IDX = DY_IDX 
WHERE DY_H_ID IS NULL