Question

我正在查看MERGE命令看起来很酷，但仍需要指定列。我正在寻找类似的东西：

MERGE INTO target AS t
USING source AS s          
WHEN MATCHED THEN
    UPDATE SET
    [all t.fields = s.fields]
WHEN NOT MATCHED THEN 
      INSERT ([all fields])
      VALUES ([all s.fields])

有可能吗？

Answer 1

我很懒...这是我编写的一个便宜的proc，会为表格吐出一般的MERGE命令。它在information_schema.columns中查询列名。我删除了我的源数据库名称 - 所以，你必须更新proc以使用你的数据库（寻找@SourceDB ......我说它很便宜。）无论如何，我知道其他人可以写得更好 - 它服务于我目的很好。（它做了一些假设，你可以把逻辑放在处理中 - 即关闭IDENTITY_INSERT - 即使表没有标识列。）它更新当前上下文中的表。它是针对sql server 2008编写的，用于同步一些表。当然，使用风险自负。

    CREATE PROCEDURE [dbo].[GenerateMergeSQL]
    @TableName varchar(100)
AS
BEGIN
    SET NOCOUNT ON 

    declare @sql varchar(5000),@SourceInsertColumns varchar(5000),@DestInsertColumns varchar(5000),@UpdateClause varchar(5000)
    declare @ColumnName varchar(100), @identityColName varchar(100)
    declare @IsIdentity int,@IsComputed int, @Data_Type varchar(50)

    declare @SourceDB as varchar(200)


    -- source/dest i.e. 'instance.catalog.owner.' - table names will be appended to this
    -- the destination is your current db context
    set @SourceDB = '[mylinkedserver].catalog.myDBOwner.'

    set @sql = ''
    set @SourceInsertColumns  = ''
    set @DestInsertColumns  = ''
    set @UpdateClause  = ''
    set @ColumnName  = ''
    set @isIdentity = 0
    set @IsComputed = 0
    set @identityColName  = ''
    set @Data_Type  = ''


DECLARE @ColNames CURSOR
SET @ColNames = CURSOR FOR 
    select column_name, COLUMNPROPERTY(object_id(TABLE_NAME), COLUMN_NAME, 'IsIdentity') as IsIdentity ,
        COLUMNPROPERTY(object_id(TABLE_NAME), COLUMN_NAME, 'IsComputed') as IsComputed , DATA_TYPE
    from information_schema.columns where table_name = @TableName order by ordinal_position

OPEN @ColNames
FETCH NEXT FROM @ColNames INTO @ColumnName, @isIdentity, @IsComputed, @DATA_TYPE

WHILE @@FETCH_STATUS = 0
    BEGIN
        if @IsComputed = 0 and @DATA_TYPE <> 'timestamp'
        BEGIN
            set @SourceInsertColumns = @SourceInsertColumns + 
                case when @SourceInsertColumns = '' THEN '' ELSE ',' end +
                'S.' + @ColumnName

            set @DestInsertColumns = @DestInsertColumns + 
                case when @DestInsertColumns = '' THEN '' ELSE ',' end +
                @ColumnName

            if @isIdentity = 0
            BEGIN
                set @UpdateClause = @UpdateClause + 
                case when @UpdateClause = '' THEN '' ELSE ',' end
                 + @ColumnName + ' = ' + 'S.' + @ColumnName + char(10)
            END

            if @isIdentity = 1 set @identityColName = @ColumnName
        END

        FETCH NEXT FROM @ColNames INTO @ColumnName, @isIdentity, @IsComputed, @DATA_TYPE
    END

CLOSE @ColNames
DEALLOCATE @ColNames

    SET @sql = 'SET IDENTITY_INSERT ' + @TableName + ' ON;
            MERGE ' + @TableName + ' AS D
                USING ' + @SourceDB + @TableName + ' AS S
                ON (D.' + @identityColName + ' = S.' + @identityColName + ')
            WHEN NOT MATCHED BY TARGET
                THEN INSERT(' + @DestInsertColumns + ') 
                VALUES(' + @SourceInsertColumns + ')
            WHEN MATCHED 
                THEN UPDATE SET 
                    ' + @UpdateClause + '
            WHEN NOT MATCHED BY SOURCE
                THEN DELETE
            OUTPUT $action, Inserted.*, Deleted.*;
            SET IDENTITY_INSERT ' + @TableName + ' OFF'

    Print @SQL

END

Answer 2

不是你想要的一切，而是部分：

WHEN NOT MATCHED THEN
INSERT的 ~~([all fields])~~
VALUES (field1, field2, ...)

（值列表必须完整，并且与表定义中字段的顺序相匹配。）

Answer 3

简单的合并替代方法，无需命名任何字段或在表设计更改时必须更新语句。从源到目标，这是单向的，但它可以是双向的。仅对更改的记录起作用，因此即使连接速度较慢的链接服务器也非常快。

--Two statement run as transaction batch
DELETE
    C
FROM
    productschina C
    JOIN 
    (select * from productschina c except select * from productsus) z
    on c.productid=z.productid

INSERT into productschina select * from productsus except select * from productschina

以下是设置要测试的表格的代码：

--Create a target table
--drop table ProductsUS
CREATE TABLE ProductsUS
(
ProductID INT PRIMARY KEY,
ProductName VARCHAR(100),
Rate MONEY
) 
GO
--Insert records into target table
INSERT INTO ProductsUS
VALUES
(1, 'Tea', 10.00),
(2, 'Coffee', 20.00),
(3, 'Muffin', 30.00),
(4, 'Biscuit', 40.00)
GO
--Create source table
--drop table productschina
CREATE TABLE ProductsChina
(
ProductID INT PRIMARY KEY,
ProductName VARCHAR(100),
Rate MONEY
) 
GO
--Insert records into source table
INSERT INTO ProductsChina
VALUES
(1, 'Tea', 10.00),
(2, 'Coffee', 25.00),
(3, 'Muffin', 35.00),
(5, 'Pizza', 60.00)
GO
SELECT * FROM ProductsUS
SELECT * FROM ProductsChina
GO

Answer 4

我认为这个答案值得更多的爱。它简单，优雅，有效。但是，根据所讨论的表格，它可能有点慢，因为except子句正在评估每一列。

我怀疑你可以通过加入主键和最后修改日期（如果存在）来节省一点时间。

DELETE
    C
FROM
    productschina C
    JOIN 
    (select primary_key, last_mod_date from productschina c except select primary_key, last_mod_date from productsus) z
    on c.productid=z.productid

INSERT into productschina select * from productsus except select * from productschina

MERGE而不在SQL Server 2008中指定列名

4 个答案: