如何使用合并在 SQL Server 中插入新行并标记没有更新和更新行的现有行

Question

我需要在 SQL Server 中创建一个存储过程并实现一个 upsert，以便它将数据从临时表（又名源）移动到最终表（又名目标）并标记新的、更新的、未更新的行或每次新一批数据进来时都被删除。我按照here的解释使用合并。

问题在于它正在更新没有任何更改的行。我的工作流程如下：

1. 将数据加载到源表中
2. 调用存储过程，根据合并条件将数据从Source 移动到Target

我的存储过程如下：

CREATE PROCEDURE [dbo].[upsert_with_flag_2]
AS
    DECLARE @current_time AS datetime
    SET @current_time = GETDATE()

    MERGE [dbo].[employee] AS Target
    USING [dbo].[employee_staging] AS Source
          ON Source.[first_name] = Target.[first_name] 
             AND Source.[last_name] = Target.[last_name] 
             AND Source.[dob] = Target.[dob]

    WHEN MATCHED
        THEN
            UPDATE 
            SET Target.[salary] = Source.[salary],
                Target.[current_address] = Source.[current_address],
                Target.[is_deleted] = 'Updated',
                Target.[processed_date] = @current_time

    WHEN NOT MATCHED BY Target 
        THEN
            INSERT ([first_name], [last_name], 
                    [dob], [salary], 
                    [current_address], [is_deleted], 
                    [processed_date])
            VALUES (Source.[first_name], Source.[last_name],
                    Source.[dob], Source.[salary], 
                    Source.[current_address], 'New',
                    @current_time);

-- After doing upsert, check for rows whose processed date is less than current date but status is new or updated, These are
-- the rows which were not present in input file. Update there status to deleted
-- QUESTION: Should we change the processed date to current date for row's whose status is deleted?

UPDATE [dbo].[employee]
SET [is_deleted] = 'deleted'
WHERE ([is_deleted] = 'New' OR [is_deleted] = 'Updated') 
  AND [processed_date] < @current_time

在此之后，我执行以下步骤来加载数据并获取输出：

--Loading the initial data
TRUNCATE TABLE [dbo].[employee_staging]
GO

INSERT INTO [dbo].[employee_staging] ([first_name], 
                                      [last_name], 
                                      [dob], 
                                      [salary], 
                                      [current_address])
VALUES  ('John', 'Doe', '1995-04-28', 3000, 'Andra Pradesh'),
        ('Robert', 'Spenser', '1994-03-28', 1800, 'Madhya Pradesh'),
        ('Vikash', 'Sharma', '1996-12-20', 1400, 'Uttar Pradesh'),
        ('Anup', 'Soni', '1994-03-28', 1800, 'Delhi'),
        ('Prijan', 'Sonar', '1989-01-28', 3000, 'Himachal Pradesh')
GO

EXEC upsert_with_flag

SELECT * FROM [dbo].[employee]

--Loading the updated data
TRUNCATE TABLE [dbo].[employee_staging]
GO

INSERT INTO [dbo].[employee_staging] ([first_name], [last_name], 
                                       [dob], [salary], 
                                       [current_address])
VALUES ('Robert', 'Spenser', '1994-03-28', 2000, 'Madhya Pradesh'),
       ('Vikash', 'Sharma', '1996-12-20', 1400, 'Maharashtra'),
       ('Anup', 'Soni', '1994-03-28', 1800, 'Delhi'),
       ('Prijan', 'Sonar', '1989-01-28', 3000, 'Himachal Pradesh'),
       ('William', 'Beck', '1991-04-22', 3300, 'Karnataka'),
       ('Robert', 'Brownie', '1986-04-22', 5000, 'Assam')

注意第 4 行和第 5 行。Anup 的输入行数据没有变化，但我仍将 [is_deleted] 列为“已更新”。我希望它类似于“现有”或“无变化”。

请帮助使这成为可能。这个 upsert 逻辑是大管道的一部分，我们需要在新文件中更新、新、未更新或删除的行。我如何做到这一点？

Answer 1

您可以在更新中的 is_deleted 字段中添加 case 语句，以检查是否有任何更改。像这样的：

MERGE [dbo].[employee] as Target
USING [dbo].[employee_stagging] as Source
ON Source.[first_name] = Target.[first_name] and
   Source.[last_name] = Target.[last_name] and
   Source.[dob] = Target.[dob]

WHEN MATCHED
THEN
    UPDATE 
    SET Target.[salary] = Source.[salary],
        Target.[current_address] = Source.[current_address],
        Target.[is_deleted] = CASE WHEN Source.salary = Target.salary
                                         AND Source.current_address = Target.current_address THEN 'No change'
                                   ELSE 'Updated'
                               END,
        Target.[processed_date] = @current_time

WHEN NOT MATCHED BY Target 
THEN
    INSERT ([first_name],
            [last_name],
            [dob],
            [salary], 
            [current_address], 
            [is_deleted],
            [processed_date])

    VALUES (Source.[first_name],
            Source.[last_name],
            Source.[dob],
            Source.[salary], 
            Source.[current_address], 
            'New',
            @current_time
            );

因此，如果更新字段与暂存数据相同，它将更新 is_deleted 为“无更改”，而如果更新字段已更改，它将更新 is_deleted到“更新”。

注意：此代码假设薪水和 current_address 是不可为空的字段（字段的表定义后跟 NOT NULL）。如果有 ARE 可以为空，那么您应该通过将 CASE 语句替换为以下内容来处理空值：

CASE WHEN (Source.salary = Target.salary
        OR Source.salary IS NULL
            AND Target.salary IS NULL)
    AND (Source.current_address = Target.current_address
        OR Source.current_address IS NULL
            AND Target.current_address IS NULL) THEN 'No change'
    ELSE 'Updated'
END

（文档here）