Question

我正在尝试从SQL Server数据库中清除旧数据（每个表中大约有5000个条目），但是由于要在另一个内部循环CURSOR，所以它花费的时间太长（一个多小时）。

BEGIN
    DECLARE @UserId int
    DECLARE @productNum varchar(50)

    DECLARE user_ids CURSOR FOR SELECT id
    FROM Users
    WHERE productId IN (SELECT ap.id 
                        FROM Account AS a, AccountProduct AS ap 
                        WHERE a.id = ap.accountId 
                          AND a.name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX'))
    
    DECLARE product_cur CURSOR FOR 
        SELECT ap.id 
        FROM Account AS a, AccountProduct AS ap
        WHERE a.id = ap.accountId 
          AND a.name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX') 
    
    OPEN user_ids

    FETCH NEXT FROM user_ids INTO @UserId

    WHILE @@FETCH_STATUS = 0
    BEGIN
        OPEN product_cur 

        FETCH NEXT FROM product_cur INTO @productNum

        WHILE @@FETCH_STATUS = 0
        BEGIN
            DELETE FROM UserRole 
            WHERE userId = @UserId 
              AND productId = (SELECT id 
                               FROM AccountProduct 
                               WHERE number = @productNum)
                
            DELETE FROM AccountProduct 
            WHERE number = @productNum

            FETCH NEXT FROM product_cur INTO @productNum
        END
        CLOSE product_cur 

        DELETE FROM Users 
        WHERE id = @UserId 
          AND accountId IN (SELECT id FROM Account 
                            WHERE name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX'))

        FETCH NEXT FROM user_ids INTO @UserId
    END

    CLOSE user_ids
    DEALLOCATE user_ids
    DEALLOCATE product_cur 
END

您知道执行此任务的更好方法吗？

Answer 1

对于评论来说，这太长了，但是，这足以给您正确的想法。但是，上面的SQL似乎不是完整的SQL，因此我无法为您提供可以提供相同行为的SQL（例如，您在room_cur中引用了游标FETCH但是，SQL语句中没有声明游标room_cur。

SQL是一种基于集合的语言，擅长基于集合的解决方案。游标不是基于不是的解决方案，它们是迭代任务，SQL Server很烂。那是设计。 SQL不是一种编程语言，因此像编程语言一样编写它意味着性能很差。

对于DELETE语句，您只需要像对待其他任何语句一样对待它，因为DELETE将从FROM返回的数据集中的已定义表中删除行。对于DELETE上的Users，（可能）这意味着您想要这样的东西：

DELETE U
FROM dbo.Users U
     JOIN dbo.Account A ON U.acccountID = A.id
WHERE A.[name] IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX');

这只是DELETE中dbo.Users的行，其中在dbo.Account中找到了连接的行，而name中的值在IN子句中。

Answer 2

您可以删除频繁提交。我建议一次在事务中删除一个用户ID并提交。

Go for batch based deletion.

DECLARE @UserIdsToDelete TABLE(RowNo int, UserId int)
DECLARE @ProductsToDelete TABLE(RowNo int, ProductId int)

INSERT INTO @UserIdsToDelete
SELECT ROW_NUMBER() OVER (ORDER BY UserId) as RowNo, UserId
    FROM Users
    WHERE productId IN (SELECT ap.id 
                        FROM Account AS a, AccountProduct AS ap 
                        WHERE a.id = ap.accountId 
                          AND a.name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX'))

INSERT INTO @productsToDelete
SELECT ROW_NUMBER() OVER (ORDER BY ap.id) as RowNo, ap.id 
        FROM Account AS a, AccountProduct AS ap
        WHERE a.id = ap.accountId 
          AND a.name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX') 


DECLARE @UserIdForDeletion INT
DECLARE @RowNoForDeletion INT = 1

SET @UserIdForDeletion = (SELECT UserID from 
@UserIdsToDelete 
WHERE RowNO = @RowNoForDeletion )
 
-- Deletion of Users
WHILE (@UserIdForDeletion IS NOT NULL )
  BEGIN

BEGIN TRY
        SET XACT_ABORT ON

        BEGIN TRANSACTION

   DELETE FROM UserRole
   WHERE UserId = @UserIdForDeletion 
   AND productId IN (SELECT ProductID from @ProductsToDelete)

    DELETE FROM Users 
        WHERE id = @UserId 
          AND accountId IN (SELECT id FROM Account 
                            WHERE name IN ('XXXXXX', 'XXXXXX', 'XXXXXX', 'XXXXXX'))

    COMMIT TRANSACTION;
    END TRY
    BEGIN CATCH

        IF XACT_STATE() <> 0 
            ROLLBACK TRANSACTION;
    
        THROW;
    END CATCH

@RowNoForDeletion += 1;
SET @UserIdForDeletion = (SELECT UserID from 
@UserIdsToDelete 
WHERE RowNO = @RowNoForDeletion )
END

-- Delete the account products
BEGIN TRY
        SET XACT_ABORT ON

        BEGIN TRANSACTION
DELETE FROM AccountProduct 
            WHERE number IN (SELECT ProductID from @ProductsToDelete)
COMMIT TRANSACTION;
    END TRY
    BEGIN CATCH

        IF XACT_STATE() <> 0 
            ROLLBACK TRANSACTION;
    
        THROW;
    END CATCH

Answer 3

不要使用游标，因为它肯定会影响查询的性能。为什么不以较小的批次执行删除操作以加快查询执行时间？ How to delete large data of table in SQL without log?

SQL Server：清理旧数据花费的时间太长

3 个答案: