Question

我有几个版本分配给DocumentID。

DocID  Version
ABC    1
ABC    2
ABC    3
DEF    1
DEF    2

如何删除旧版本并保留最新版本？删除后，这应保留在表中：

DocID  Version
ABC    3
DEF    2

Answer 1

SQL Server 2005 +：

;WITH x AS (SELECT DocID, Version, rn = ROW_NUMBER() OVER 
  (PARTITION BY DocID ORDER BY Version DESC)
  FROM dbo.tablename
)
DELETE x WHERE rn > 1;

对于SQL Server 2000，它有点复杂。（包含版本信息总是有用的。）

DELETE t
FROM dbo.tablename AS t
LEFT OUTER JOIN 
(
  SELECT DocID, Version = MAX(Version)
  FROM dbo.tablename
  GROUP BY DocID
) AS t2
ON t.DocID = t2.DocID
AND t.Version = t2.Version
WHERE t2.DocID IS NULL;

显然是后一个查询will work in MySQL as well（感谢@bluefeet）。

~~对于MySQL，你可以自己做一个完全不同的问题。~~

删除旧版本条目的声明

1 个答案: