Question

我有一个包含三列的表 correlation 。

相关

user1   user2   corr

此表包含所有用户对的相关值。

我需要更新另一个表中所有对的 corr 值。

我使用的查询是：

UPDATE correlation
SET corr = (SELECT ROUND((COUNT(*) * SUM(x.rating * y.rating) - SUM(x.rating) * SUM(y.rating)) /
                   (SQRT(COUNT(*) * SUM(SQUARE(x.rating)) - SQUARE(SUM(x.rating))) * SQRT(COUNT(*) 
                     * SUM(SQUARE(y.rating)) - SQUARE(SUM(y.rating)))), 2) 
            FROM            users AS x INNER JOIN
                     users AS y ON x.itemID = y.itemID
            WHERE        (x.userID = @user1) AND (y.userID = @user2)))
WHERE user1 = @user1 and user2 = @user2

如何使用过程执行此查询？

我首先从关联表中检索所有用户对。

SELECT user1, user2 from correlation

如何使用此查询的结果，对于返回的每一行，执行更新查询？

相关表中有大约200万行。

我尝试使用SqlDataReader（没有任何存储过程）在C＃代码中执行此操作，但这花费的时间太长了。 SqlDataReader将读取所有行，并且对于每行读取它将执行更新查询。

Answer 1

是否要更新关联表中的所有记录？像这样：

UPDATE correlation
   SET corr = (SELECT ROUND((COUNT(*) * SUM(x.rating * y.rating) - SUM(x.rating) * SUM(y.rating)) /
                      (SQRT(COUNT(*) * SUM(SQUARE(x.rating)) - SQUARE(SUM(x.rating))) * SQRT(COUNT(*) 
                      * SUM(SQUARE(y.rating)) - SQUARE(SUM(y.rating)))), 2) 
                 FROM users AS x
           INNER JOIN users AS y
                   ON x.itemID = y.itemID
                WHERE (x.userID = user1) AND (y.userID = user2)))

或者

    UPDATE c
       SET corr = z.corr
      FROM correlation c
INNER JOIN (SELECT ROUND((COUNT(*) * SUM(x.rating * y.rating) - SUM(x.rating) * SUM(y.rating)) /
                          (SQRT(COUNT(*) * SUM(SQUARE(x.rating)) - SQUARE(SUM(x.rating))) * SQRT(COUNT(*) 
                          * SUM(SQUARE(y.rating)) - SQUARE(SUM(y.rating)))), 2) AS corr,
                   x.userID AS user1, y.userID AS user2
              FROM users AS x
        INNER JOIN users AS y
                ON x.itemID = y.itemID
          GROUP BY x.userID, y.userID) AS z
        ON z.user1 = c.user1 AND z.user2 = c.user2

Answer 2

你可以做三件事：

使用批量插入/更新或here中的其他技术。
使用CLR SP（所以，你以后会在c＃中快乐地写它，然后将它作为存储过程插入到数据库中，你可以运行它）。详情请见 MSDN。
使用普通的旧SQL，但由于我不是SQL母版，我会留下此选项供其他人回答

Answer 3

如果要从数据库表中检索数据并将其发送回数据库，那么我建议创建SP，SP将为您执行相同的操作。

 CREATE PROCEDURE [Procedure_Name]

 AS

 BEGIN

 declare @user1  int
 declare @user2 int
 declare cur CURSOR LOCAL for

 SELECT user1, user2 from correlation 

 open cur

 fetch next from cur into @user1, @user2

 while @@FETCH_STATUS = 0 BEGIN

 UPDATE correlation
 SET corr = (SELECT ROUND((COUNT(*) * SUM(x.rating * y.rating) - SUM(x.rating) *         SUM(y.rating)) /
               (SQRT(COUNT(*) * SUM(SQUARE(x.rating)) - SQUARE(SUM(x.rating))) * SQRT(COUNT(*) 
                 * SUM(SQUARE(y.rating)) - SQUARE(SUM(y.rating)))), 2) 
        FROM            users AS x INNER JOIN
                 users AS y ON x.itemID = y.itemID
        WHERE        (x.userID = @user1) AND (y.userID = @user2)))
        WHERE user1 = @user1 and user2 = @user2

 --If you have Sp to perform above put your SP 
 --execute your SP with user1, user2 on each row
 --For example exec uspYourSP @user1, @user2

 fetch next from cur into @user1, @user2
END

close cur
deallocate cur

END

现在一旦你的SP到位，你只需要从C＃调用SP而不需要任何参数。这将改善您的表现，因为我们正在从CURSOR获取记录。

SQL Server：如何使用存储过程中的查询结果

3 个答案: