合并不插入新值

Question

我正在尝试使用 MERGE 向 table 插入新值，前提是它们不存在于同一个 table。

这是我正在使用的查询：

MERGE [dbo].[TARGET_TABLE] AS Target 
USING 
(SELECT [NAME]
    FROM [dbo].[TARGET_TABLE] 
    WHERE [NAME]='ThisValuesDoesntExists' AND [STATUS] IS NULL) AS Source
    ON Target.[NAME]= Source.[NAME]
WHEN NOT MATCHED
    THEN INSERT ([NAME],[file_first_upload],[upload_date])
        VALUES('ThisValuesDoesntExists',1,DEFAULT);

但是当我执行它时，我收到一条消息（0 行受影响）。

如果我执行“源”查询，我得到 0 行。

SELECT [NAME] 
FROM [dbo].[TARGET_TABLE] 
WHERE [NAME] = 'ThisValuesDoesntExists' AND [STATUS] IS NULL

我做错了什么？

谢谢

Answer 1

如果您查看 MERGE 文档，您会发现源数据必须存在才能匹配（或不匹配）目标中的现有行 table:

WHEN NOT MATCHED [ BY TARGET ] THEN <merge_not_matched>

Specifies that a row is inserted into target_table for every row returned by <table_source> ON <merge_search_condition> that doesn't match a row in target_table, but satisfies an additional search condition, if present. The values to insert are specified by the <merge_not_matched> clause. The MERGE statement can have only one WHEN NOT MATCHED [ BY TARGET ] clause.

您面临的问题是您的“源”数据未返回任何内容，因此 MERGE 查询没有可匹配或插入的内容。

下面的示例代码进行演示：

IF OBJECT_ID('dbo.TARGET_TABLE', 'U') IS NOT NULL DROP TABLE dbo.TARGET_TABLE 
GO 

CREATE TABLE TARGET_TABLE ([Name] VARCHAR(100), file_first_upload BIT, upload_date DATETIME, [STATUS] VARCHAR(100)) 

MERGE [dbo].[TARGET_TABLE] AS Target 
USING 
(SELECT [NAME]
    FROM [dbo].[TARGET_TABLE] 
    WHERE [NAME]='ThisValuesDoesntExists' AND [STATUS] IS NULL) AS Source
    ON Target.[NAME]= Source.[NAME]
WHEN NOT MATCHED
    THEN INSERT ([NAME],[file_first_upload],[upload_date])
        VALUES('ThisValuesDoesntExists',1,DEFAULT);

SELECT * 
FROM TARGET_TABLE 

MERGE [dbo].[TARGET_TABLE] AS Target 
USING (VALUES ('ThisValuesDoesntExistss',1,GETDATE())) AS Source ([Name], [file_first_upload],[upload_date])
ON Target.[NAME] = Source.[Name] 
WHEN NOT MATCHED
    THEN INSERT ([NAME],[file_first_upload],[upload_date]) VALUES (Source.[Name], Source.file_First_upload, Source.upload_date);

SELECT * 
FROM TARGET_TABLE

合并不插入新值

Merge not inserting new values

sql

tsql

sql-server

sql-merge

sql-server-2017