DML_Data Modification_MERGE

DML_8-Data Modification_MERGE (将Source表合并到Target)

语法：
MERGE INTO 目标表
USING 源表
WHEN MATCHED AND
                                 (Condition) THEN
        UPDATE SET
              目标表.Field1 = 源表.Field1,
           目标表.Field2 = 源表.Field2,
           ...... 
WHEN NOT MATCHED
        INSERT (Field1, Field2, ...)
        VALUES(VALUE1, VALUE2, ...)
WHEN NOT MATCHED BY SOURCE THEN         --假使有此逻辑
        DELETE...     ;                                           --假使需要这么做 (Note:   semicolon不能遗漏)

/*
    MERGE语句的用法
*/
-----------------------------------------------------------------------------------------
--表1.Customers
use testdb
IF OBJECT_ID('dbo.Customers','U') IS NOT NULL DROP TABLE dbo.Customers;
CREATE TABLE dbo.Customers
(
    custid int NOT NULL,
    companyname VARCHAR(25) NOT NULL,
    phone VARCHAR(20) NOT NULL,
    address VARCHAR(50) NOT NULL,
        CONSTRAINT PK_Customers PRIMARY KEY(custid)
)
INSERT INTO dbo.Customers(custid,companyname,phone,address)
VALUES (1,'CUST_1','(111) 111-1111','address 1'),
       (2,'CUST_2','(222) 222-2222','address 2'),
       (3,'CUST_3','(333) 333-3333','address 3'),
       (4,'CUST_4','(444) 444-4444','address 4'),
       (5,'CUST_5','(555) 555-5555','address 5');
-----------------------------------------------------------------------------------------
--表2.CustomersStage
IF OBJECT_ID('dbo.CustomersStage','U') IS NOT NULL DROP TABLE dbo.CustomersStage;
CREATE TABLE dbo.CustomersStage
(
    custid int NOT NULL,
    companyname VARCHAR(25) NOT NULL,
    phone VARCHAR(20) NOT NULL,
    address VARCHAR(50) NOT NULL,
        CONSTRAINT PK_CustomersStage PRIMARY KEY(custid)
)
INSERT INTO dbo.CustomersStage(custid,companyname,phone,address)
VALUES (2,'AAAAA','(222) 222-2222','address 2'),
       (3,'CUST_3','(333) 333-3333','address 3'),
       (5,'BBBBB','CCCCC','DDDDD'),
       (6,'cust_6 (new)','(666) 666-6666','address 6'),
       (7,'cust_7 (new)','(777) 777-7777','address 7');
-----------------------------------------------------------------------------------------
SELECT * FROM dbo.Customers
SELECT * FROM dbo.CustomersStage
-----------------------------------------------------------------------------------------
--3.Merge语句 without And condition
MERGE INTO dbo.Customers AS TGT
USING dbo.CustomersStage AS SRC
   ON TGT.custid = SRC.custid
WHEN MATCHED THEN                        --此处没有其他条件，即使来源表与目标表完全相同，也要更新目标表
      UPDATE SET
           TGT.companyname = SRC.companyname,
           TGT.phone = SRC.phone,
           TGT.address = SRC.address
WHEN NOT MATCHED THEN
      INSERT (custid, companyname, phone, address)
      VALUES (SRC.custid,SRC.companyname, SRC.phone, SRC.address);
----------------
Note (此处试验是加了分号结束的，只是为了强调一下必须要以分号结束):
        Msg 10713, Level 15, State 1, Line 53
        A MERGE statement must be terminated by a semi-colon (;).
-----------------------------------------------------------------------------------------
----4.Merge语句 without And condition, WHEN NOT MATCHED BY SOURCE THEN
MERGE INTO dbo.Customers AS TGT
USING dbo.CustomersStage AS SRC
   ON TGT.custid = SRC.custid
WHEN MATCHED THEN
      UPDATE SET
           TGT.companyname = SRC.companyname,
           TGT.phone = SRC.phone,
           TGT.address = SRC.address
WHEN NOT MATCHED THEN
      INSERT (custid, companyname, phone, address)
      VALUES (SRC.custid,SRC.companyname, SRC.phone, SRC.address)
WHEN NOT MATCHED BY SOURCE THEN
     DELETE;
----------------
--在上一次已经合并的基础上，再次进行合并，所以此处显示5行被合并，2行被删除
(7 row(s) affected)
-----------------------------------------------------------------------------------------
--
--5.Merge语句 with And condition
MERGE INTO dbo.Customers AS TGT
USING dbo.CustomersStage AS SRC
   ON TGT.custid = SRC.custid
WHEN MATCHED AND                        --
              (TGT.companyname <> SRC.companyname
           or TGT.phone <> SRC.phone
            or TGT.address <> SRC.address) THEN
      UPDATE SET
           TGT.companyname = SRC.companyname,
           TGT.phone = SRC.phone,
           TGT.address = SRC.address
WHEN NOT MATCHED THEN
      INSERT (custid, companyname, phone, address)
      VALUES (SRC.custid,SRC.companyname, SRC.phone, SRC.address);
-----------------------------------------------------------------------------------------
 
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建立的2个测试表查询的数据：
         
合并后的数据：