用最小日期更新临时表

Question

仅在存在较早的插入日期的情况下，我才尝试为#tmpResults表中的所有不同AccId和AccNameHolder组合更新InsertDate 。

表模式如下所示：

#tmp结果

Trans | AccId | AccountNameHolder | EarlyDate | CardType 

PositionCollection

Id | AccId | InsertDate | BtchId

CardErrors

AccId | AccNameHolder | BtchId | TransId

到目前为止，这是我尝试过的：

UPDATE  RES  
SET     EarlyDate = pc.InsertDate   
FROM  ( dbo.PositionCollection pc    
        LEFT JOIN dbo.CardErrors ce ON ce.BtchId = pc.BtchId AND pc.id =     ce.Transid  )    
    INNER JOIN #tmpResults RES   
ON      RES.AccId = pc.AccId    
AND     RES.AccNameHolder = ce.AccNameHolder    
WHERE   RES.EarlyDate = (SELECT MIN(InsertDate) FROM PostionCollection)    
AND     RES.AccId = pc.AccId    
AND     RES.AccNameHolder = ce.AccNameHolder

Answer 1

这是一些更通用的解决方案，对于InsertDate为null的情况，您可以将它们与DateDiff一起使用，以将条件更改为更早，更高或任何类似的条件

OldInstDate <= COALESCE(NewInstDate, OldInstDate)

可以在select语句中实现条件更新，因此...

SET InsertDate = COALESCE(InsertDate, NewInsertDate) WHERE...

要么

SET InsertDate = CASE WHEN InsertDate IS NULL THEN NewInsertDate 
                      ELSE InsertDate END

要么

WHERE ...
AND InsertDate IS NULL

对于子查询http://allenbrowne.com/subquery-01.html的真正清晰的帮助，我认为这可能是我见过的最好的查询了， http：//allenbrowne.com/subquery-02.html可以解决问题

Answer 2

在UPDATE语句中使用派生表

UPDATE x
SET x.EarlyDate = x.InsertDate  
FROM  ( 
       SELECT RES.EarlyDate, pc.InsertDate
       FROM dbo.PositionCollection pc
         LEFT JOIN dbo.CardErrors ce ON ce.BtchId = pc.BtchId AND pc.id = ce.Transid
         INNER JOIN #tmpResults RES ON RES.AccId = pc.AccId
           AND RES.AccNameHolder = ce.AccNameHolder
       WHERE RES.EarlyDate = (SELECT MIN(InsertDate) FROM PostionCollection) AND RES.AccId = pc.AccId
         AND RES.AccNameHolder = ce.AccNameHolder
       ) x

更新27.11.2012

UPDATE x
SET x.EarlyDate = x.InsertDate
FROM  (
       SELECT RES.EarlyDate, m.InsertDate
       FROM dbo.PositionCollection pc
         LEFT JOIN dbo.CardErrors ce ON ce.BtchId = pc.BtchId AND pc.id = ce.Transid
         INNER JOIN #tmpResults RES ON RES.AccId = pc.AccId AND RES.AccNameHolder = ce.AccNameHolder
         INNER JOIN (SELECT MIN(InsertDate) AS InsertDate FROM PostionCollection) m
           ON RES.EarlyDate = m.InsertDate 
       ) x