MERGE INTO

Posted 2021-02-14 binbingo

USE tempdb;
GO
IF OBJECT_ID(‘SourceTable‘) IS NOT NULL
    DROP TABLE SourceTable;
IF OBJECT_ID(‘TargetTable‘) IS NOT NULL
    DROP TABLE TargetTable;

--源
CREATE TABLE SourceTable
(
    id INT,
    name VARCHAR(2),
    [desc] NVARCHAR(50)
);
--目标
CREATE TABLE TargetTable
(
    id INT,
    name VARCHAR(2),
    [desc] NVARCHAR(50)
);

--源表数据
INSERT INTO SourceTable
VALUES
(1, ‘a‘, ‘描述1‘),
(2, ‘a‘, ‘描述2‘),
(3, ‘a‘, ‘描述3‘),
(4, ‘a‘, ‘描述4‘);

--目标表数据
INSERT INTO TargetTable
VALUES
(1, ‘a‘, ‘在源表里存在，将会被更新‘);
INSERT INTO TargetTable
VALUES
(2, ‘a‘, ‘在源表里存在，将会被更新‘);
INSERT INTO TargetTable
VALUES
(5, ‘a‘, ‘在源表里不存在，将会被删除‘);
INSERT INTO TargetTable
VALUES
(6, ‘b‘, ‘在源表里不存在，但是条件不符合,不删除‘);

SELECT *
FROM SourceTable AS st;
/*
id name    desc
1    a 描述1
2    a 描述2
3    a 描述3
4    a 描述4
*/

SELECT *
FROM TargetTable AS tt;
/*
id    name desc
1    a 在源表里存在，将会被更新
2    a 在源表里存在，将会被更新
5    a 在源表里不存在，将会被删除
6    b 在源表里不存在，但是条件不符合,不删除
*/

--注意事项 
--1.最后的分号必须有
--2.源表可以是一个具体的表,也可以是一个子查询语句
--3.2008或以上版本才有的功能

MERGE INTO TargetTable AS T --可添加 TOP 限制操作行数: MERGE TOP(2)
USING SourceTable AS S
ON T.id = S.id
   AND T.name = ‘a‘
   AND S.name = ‘a‘
WHEN MATCHED --当两者的id能匹配，id=1,2的数据被更新
THEN    UPDATE SET T.[desc] = S.[desc]
WHEN NOT MATCHED --目标表没有的ID, 在原表中有，则插入相关的数据
THEN    INSERT (id,name) VALUES (S.id, S.name)
WHEN NOT MATCHED BY SOURCE  AND t.name = ‘a‘ --目标表中存在，源表不存在，则删除
THEN    DELETE
OUTPUT $ACTION AS [Action],
       INSERTED.id AS [插入的id],
       Inserted.name AS [插入的name],
       INSERTED.[desc] AS [插入的DESC],
       DELETED.id AS [删除的id],
       DELETED.name AS [删除的name],
       DELETED.[desc] AS [删除的DESC];




SELECT *
FROM SourceTable AS st;


SELECT *
FROM TargetTable AS tt;