如何在更新的表上使用多個聯接更新SQL Server上的表？ （FROM FROM JOIN）

Question

如何在更新的表上使用多個聯接更新SQL Server上的表？ 在MySQL中，您可以爲更新的表定義別名，但它如何與TSQL協同工作。

UPDATE recert.ou    --#1-- In MSSQL/TSQL no alias allowed 
SET parent_id = o2.ID 
    FROM recert.ou as O    
    JOIN recert.country C ON C.ID = O.country_id 
    JOIN recert.ou P ON O.parent_id = P.ID and p.country_id <> O.country_id  
    JOIN recert.ou o2 on o2.name = p.name and c.ID = o2.country_id    
    JOIN recert.country as c2 on c2.ID = o2.country_id 
      WHERE O.ID = o2.ID 

-

RESULT: *The table 'o' is ambiguous.* 

Answer 1

This works on Sql Fiddle刪除別名。

UPDATE o 
SET parent_id = o2.ID 
    FROM recert O 
    JOIN c C ON C.ID = O.country_id 
    JOIN recert P ON O.parent_id = P.ID and p.country_id <> O.country_id 
    JOIN recert o2 on o2.name = p.name and c.ID = o2.country_id 
    JOIN c c2 on c2.ID = o2.country_id 
WHERE O.ID = o2.ID 

我想這個問題的出現是因爲您試圖重新別名別名，但我不確定。

Answer 2

您可以將所有的東西都WHERE子句：

UPDATE o    --#1-- In MSSQL/TSQL no alias allowed 
    SET parent_id = o2.ID 
    FROM c, o, o o2, C c2 
    Where o.country_id = c.id and o.parent_id = p.id and p.country_id <> O.country_id and 
      o2.name = p.name and c.ID = o2.country_id and c2.ID = o2.country_id 

這是不我喜歡加入的風格，但它應該能滿足你的目的。

但是，TSQL，我真的做到以下幾點。創建一個返回每個id的新更新值的查詢。然後編寫一個查詢，格式如下：

with toupdate as (<the query>) 
    update o 
     set o.parent_id = toupdate.id 
    from toupdate 
    where o.id = toupdate.id  

Answer 3

你只需要爲O表

UPDATE o    
SET parent_id = o2.ID 
FROM o    
JOIN c C ON C.ID = o.country_id 
JOIN o P ON o.parent_id = P.ID and p.country_id <> o.country_id 
JOIN o o2 on o2.name = p.name and c.ID = o2.country_id    
JOIN c c2 on c2.ID = o2.country_id 
WHERE o.ID = o2.ID