在SQL Server 2008 MERGE语法中使用什么？

Question

雅各布问了一个完美的问题:给我MERGE语法.

那里的每一个答案都会立即跳到他们能想到的最复杂的案例中; 用无关的混淆来掩盖语法.

马克给出了答案:

MERGE 
   member_topic AS target
USING 
   someOtherTable AS source
ON 
   target.mt_member = source.mt_member 
   AND source.mt_member = 0 
   AND source.mt_topic = 110
WHEN MATCHED THEN 
   UPDATE SET mt_notes = 'test'
WHEN NOT MATCHED THEN 
   INSERT (mt_member, mt_topic, mt_notes) VALUES (0, 110, 'test')
; 

看着这个答案,我和雅各布一样困惑:

我没有someOtherTable

Marc建议这someOtherTable是一个虚拟的占位符值 - 没有那个表并不重要.

我尝试了,SQL Server 确实抱怨

无效的对象名称'someOtherTable'.

这使我努力理解什么USING的USING foo是对,如果它不是重要的(除了实际上很重要).

是什么USING时,它的使用使用富时我使用SQL Server 2008合并语法？

---

奖金问题

什么是使用MERGE的UPSERT语法:

IF (rowExists)
   UPDATE Users SET Firstname='Ian', LastName='Boyd' WHERE Username='iboyd'
ELSE
   INSERT INTO Users (UserGUID, Username, FirstName, LastName, AuthenticationMethod)
   VALUES ('{77410DC5-7A3E-4F1A-82C6-8EFB3068DE66}', 'iboyd', 'Ian', 'Boyd', 'Windows')

变成(我试过的确切代码):

begin transaction

    MERGE 
       Users
    USING 
       foo
    ON  
       Users.UserName = foo.UserName
    WHEN MATCHED THEN
        UPDATE SET Firstname = foo.FirstName, Lastname = foo.LastName
    WHEN NOT MATCHED THEN
        INSERT (UserGUID, Username, FirstName, LastName, AuthenticationMethod)
        VALUES ('{77410DC5-7A3E-4F1A-82C6-8EFB3068DE66}', 'iboyd', 'Ian', 'Boyd', 'Windows')
    ; --A MERGE statement must be terminated by a semi-colon (;).

rollback

Msg 208, Level 16, State 1, Line 3
Invalid object name 'foo'.

？

使用Users包含列的表:

UserGUID uniqueidentifier
Username varchar(50)
FirstName varchar(50)
LastName varchar(50)
AuthenticationMethod varchar(50)

---

更新:

USING <table_source> 

在哪里table_source:

table_or_view_name [ [ AS ] table_alias ] [ <tablesample_clause> ] 
    [ WITH ( table_hint [ [ , ]...n ] ) ] 
| rowset_function [ [ AS ] table_alias ] 
    [ ( bulk_column_alias [ ,...n ] ) ] 
| user_defined_function [ [ AS ] table_alias ]
| OPENXML <openxml_clause> 
| derived_table [ AS ] table_alias [ ( column_alias [ ,...n ] ) ] 
| <joined_table> 
| <pivoted_table> 
| <unpivoted_table> 

在哪里joined_table:

未定义

在哪里pivoted_table:

未定义

在哪里unpivoted_table:

未定义

Answer 1

合并具有表源和目标表.这引入了源表(不一定是实际的物理表,只是结果集).

语法在你的问题中表明.要从另一个表或视图合并使用

MERGE 
   Users
USING SomeOtherTableName AS foo /*Alias is optional*/
ON /* ... */

或者你可以使用<unpivoted_table>例如

MERGE 
   Users
USING master..spt_values
UNPIVOT (X FOR Y IN ([high],[low])) AS foo 
ON  
   Users.Username = foo.Y 
WHEN MATCHED THEN
    UPDATE SET FirstName = foo.Y
WHEN NOT MATCHED THEN
    INSERT (UserGUID, Username, FirstName, LastName, AuthenticationMethod)
    VALUES (foo.Y, foo.Y, foo.Y, foo.Y, foo.Y);

对于您的奖金问题,您可以使用VALUES此处的条款作为derived_table选项的一部分.

MERGE Users
USING (VALUES ('{77410DC5-7A3E-4F1A-82C6-8EFB3068DE66}',
      'iboyd',
      'Ian',
      'Boyd',
      'Windows')) AS foo(UserGUID, Username, FirstName, LastName, AuthenticationMethod)
ON Users.UserName = foo.UserName
WHEN MATCHED THEN
  UPDATE SET Firstname = foo.FirstName,
             Lastname = foo.LastName
WHEN NOT MATCHED THEN
  INSERT (UserGUID,
          Username,
          FirstName,
          LastName,
          AuthenticationMethod)
  VALUES (UserGUID,
          Username,
          FirstName,
          LastName,
          AuthenticationMethod); 

Answer 2

源表可以是任何内容,例如:

MERGE 
   member_topic AS target
USING 
   (SELECT @Variable1, @Variable2, @Variable3) AS source(Col1, Col2, Col3)
ON 
   target.mt_member = source.Col1 
   AND source.Col1 = 0 
   AND source.Col2 = 110
WHEN MATCHED THEN 
   UPDATE SET mt_notes = 'test'
WHEN NOT MATCHED THEN 
   INSERT (mt_member, mt_topic, mt_notes) VALUES (0, 110, 'test');

显然,在嵌套源代码中你可以做更多的事情.从视图,函数,表变量,CTE中选择均匀.

至于奖金问题,你回答了自己的问题.

有时候,对于非常大的表,我也使用ROWLOCK目标表上的提示,至少在更新的情况下尽量不要锁定整个表:

MERGE 
   member_topic WITH (ROWLOCK) AS target

与奖金问题无关,这是一个工作样本.当然,我重命名了一些对象.

DECLARE @Variable1 AS INT;
SET @Variable1 = 1234;

MERGE dbo.Table1 WITH(ROWLOCK) target
USING(SELECT @Variable1) source(Key)
ON target.[Key] = source.[Key]
WHEN MATCHED THEN
    UPDATE SET
    Col1 = @SomeVar1,
    Col2 = @SomeVar2
WHEN NOT MATCHED THEN
INSERT 
        ([Key]
        ,[Col1]
        ,[Col2])
    VALUES
        (@Variable1
        ,@SomeVar1
        ,@SomeVar2);