只更新SQL Server中重複條目的第一條記錄

Question

我需要幫助來嘗試更新具有多個重複記錄的表，但我被卡住了。

我有這張表，我需要更新im_cust9與alt_item_id1值。

我使用來從表中該結果的查詢如下：

SELECT 
    o.item_id, o.alt_item_id1, o.im_cust9, o.owner_id, o.if_updatestamp 
FROM 
    item_master o 
INNER JOIN 
    (SELECT 
      alt_item_id1, COUNT(*) AS dupeCount 
     FROM 
      item_master 
     WHERE 
      owner_id = 'GIII' AND alt_item_id1 <> '' 
     GROUP BY 
      alt_item_id1 
     HAVING 
      COUNT(*) > 1) oc ON o.alt_item_id1 = oc.alt_item_id1 
WHERE 
    owner_id = 'GIII' AND o.alt_item_id1 <> '' 
ORDER BY 
    alt_item_id1, if_updatestamp ASC 

不知道如何更新每個組副本alt_item_id1的最古老的記錄

我使用SQL Server 2012

任何幫助，不勝感激！

Answer 1

要獲取最新的行更新，請使用if_updatestamp的最大值。爲最老的使用最小值。然後，它加入到你的表像這樣的UDPATE ...

update IM 
Set IM.im_cust9 = NewDupeRow.alt_item_id1 
From item_master IM 
JOIN ( 
SELECT alt_item_id1,Max(if_updatestamp) MaxUpdateValue 
FROM item_master WHERE owner_id='GIII' AND alt_item_id1<>'' 
GROUP BY alt_item_id1) NewDupeRow 
On IM.alt_item_ID = NewDupeRow.alt_item_ID 
AND IM.if_updatedstamp = NewDupeRow.MaxUpdateValue 

Answer 2

可以使用可更新的CTE和row_number()做到這一點：

with toupdate as (
     select i.*, 
      row_number() over (partition by alt_item_id order by if_updatestamp) as seqnum 
     from item_master i 
    ) 
update toupdate 
    set im_cust9 = alt_item_id1 
    where seqnum = 1;