MSSQL 与分布式事务替代方案合并

Question

我有一个分布式事务，我需要合并到目标远程表中。 现在根据 MSDN 不允许 MERGE INTO：“target_table 不能是远程表”。

所以我的解决方法如下： 0. 开始分布式事务 1. 定义一个游标 2. 打开它 3. 如果游标至少有一条记录 (CURSOR_STATUS()=1) 获取下一个 4. 如果存在（选择顶部 1 * from target_remote_table where id = @myCurrentCursorId) -> 当 true 更新 target_remote_table 当 false 插入 target_remote_table 5. 提交/回滚分布式事务取决于 trancount 和 xact_state

它有效，但我知道游标是邪恶的，你不应该使用它们。所以我想问一下是否有其他方法可以通过不使用游标来解决这个问题？

USE [My_DB]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE [dbo].[my_proc_merge_into_remote_table]
@ID_A INT, 
@ID_B INT

AS
BEGIN
SET NOCOUNT ON;

-- CURSOR VALUES
DECLARE @field_A INT
DECLARE @field_B INT
DECLARE @field_C INT
DECLARE @field_D BIT
DECLARE @field_E INT
DECLARE @field_F DATETIME
DECLARE @field_G VARCHAR(20)
DECLARE @field_H DATETIME
DECLARE @field_I VARCHAR(20)


 BEGIN TRY

    BEGIN DISTRIBUTED TRANSACTION 

    -- CURSOR !!
    DECLARE my_cursor CURSOR FOR 
    SELECT      b.field_A , 
                b.field_B,
                c.field_C,
                a.field_D, 
                a.field_E,
                GETDATE() AS field_F,
                a.field_G, 
                GETDATE() AS field_H, 
                a.field_I
         FROM dbo.source_tbl a
         LEFT JOIN dbo.base_element_tbl l 
            ON a.obj_id = l.obj_id AND a.element_id = l.element_id 
         INNER JOIN dbo.base_obj_tbl b 
            ON a.obj_id = b.obj_id 
         INNER JOIN dbo.element_tbl c 
            ON a.element_id = c.element_id 
         WHERE a.ID_B = @ID_B
            AND a.ID_A = @ID_A;


    OPEN my_cursor;


    -- check if cursor result set has at least one row
    IF CURSOR_STATUS('global', 'my_cursor') = 1 BEGIN   

        FETCH NEXT FROM my_cursor 
           INTO @field_A,
                @field_B,
                @field_C,
                @field_D,
                @field_E,
                @field_F,
                @field_G,
                @field_H,
                @field_I;


        WHILE @@FETCH_STATUS = 0 BEGIN
            -- HINT: MY_REMOTE_TARGET_TABLE is a Synonym which already points to the correct database and table
            IF EXISTS(SELECT TOP 1 * FROM MY_REMOTE_TARGET_TABLE WHERE field_A = @field_A AND field_B = @field_B AND field_C = @field_C AND field_E = @field_E)
                UPDATE MY_REMOTE_TARGET_TABLE SET field_D = @field_D, field_H = @field_H, field_I = @field_I;
            ELSE 
                INSERT INTO MY_REMOTE_TARGET_TABLE (field_A, field_B, field_C, field_D, field_E, field_F, field_G, field_H, field_I) VALUES (@field_A, @field_B, @field_C, @field_D, @field_E, @field_F, @field_G, @field_H, @field_I);

            FETCH NEXT FROM my_cursor 
               INTO @field_A,
                    @field_B,
                    @field_C,
                    @field_D,
                    @field_E,
                    @field_F,
                    @field_G,
                    @field_H,
                    @field_I;

        END;
    END;

    CLOSE my_cursor;
    DEALLOCATE my_cursor;


    IF (@@TRANCOUNT > 0 AND XACT_STATE() = 1)
    BEGIN
        COMMIT TRANSACTION 
    END     


END TRY
BEGIN CATCH
  IF (@@TRANCOUNT > 0 AND XACT_STATE() = -1)        
    ROLLBACK TRANSACTION

END CATCH;

END

Answer 1

在这里，首先要更新内部联接目标和源，然后缺少要插入的左侧联接。

;WITH CTE_Source AS 
(   
    SELECT  b.field_A , 
            b.field_B,
            c.field_C,
            a.field_D, 
            a.field_E,
            GETDATE() AS field_F,
            a.field_G, 
            GETDATE() AS field_H, 
            a.field_I
         FROM dbo.source_tbl a
         LEFT JOIN dbo.base_element_tbl l 
            ON a.obj_id = l.obj_id AND a.element_id = l.element_id 
         INNER JOIN dbo.base_obj_tbl b 
            ON a.obj_id = b.obj_id 
         INNER JOIN dbo.element_tbl c 
            ON a.element_id = c.element_id 
         WHERE a.ID_B = @ID_B
            AND a.ID_A = @ID_A;
)
UPDATE trgt
SET trgt.field_D = src.field_D, trgt.field_H = src.field_H, trgt.field_I = src.field_I
FROM MY_REMOTE_TARGET_TABLE trgt
INNER JOIN CTE_Source src ON src.field_A = trgt.field_A AND src.field_B = trgt.field_B AND src.field_C = trgt.field_C AND src.field_E = trgt.field_E


;WITH CTE_Source AS 
(   
    SELECT  b.field_A , 
            b.field_B,
            c.field_C,
            a.field_D, 
            a.field_E,
            GETDATE() AS field_F,
            a.field_G, 
            GETDATE() AS field_H, 
            a.field_I
         FROM dbo.source_tbl a
         LEFT JOIN dbo.base_element_tbl l 
            ON a.obj_id = l.obj_id AND a.element_id = l.element_id 
         INNER JOIN dbo.base_obj_tbl b 
            ON a.obj_id = b.obj_id 
         INNER JOIN dbo.element_tbl c 
            ON a.element_id = c.element_id 
         WHERE a.ID_B = @ID_B
            AND a.ID_A = @ID_A;
)
INSERT INTO MY_REMOTE_TARGET_TABLE (field_A, field_B, field_C, field_D, field_E, field_F, field_G, field_H, field_I) 
SELECT field_A, field_B, field_C, field_D, field_E, field_F, field_G, field_H, field_I 
FROM CTE_Soure src
LEFT JOIN MY_REMOTE_TARGET_TABLE trgt ON src.field_A = trgt.field_A AND src.field_B = trgt.field_B AND src.field_C = trgt.field_C AND src.field_E = trgt.field_E
WHERE trgt.field_A IS NULL