MERGE without specifying column names in SQL Server 2008 - sql-server

Question

I was looking at the MERGE command which seems cool but still it requires the columns to be specified. I'm looking for something like:
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])
Is it possible?

Answer 1

I'm lazy... this is a cheap proc I wrote that will spit out a general MERGE command for a table. It queries information_schema.columns for column names. I ripped out my source database name - so, you have to update the proc to work with your database (look for #SourceDB... I said it was cheap.) Anyway, I know others could write it much better - it served my purpose well. (It makes a couple assumptions that you could put logic in to handle - namely turning IDENTITY_INSERT OFF - even when a table doesn't have identity columns.) It updates the table in your current context. It was written against sql server 2008 to sync up some tables. Use at your own risk, of course.
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

Not everything you wanted, but partially:
WHEN NOT MATCHED THEN
INSERT([all fields])
VALUES (field1, field2, ...)
(The values list has to be complete, and match the order of the fields in your table's definition.)

Answer 3

Simple alternative to merge without naming any fields or having to update statement whenever table design changes. This is uni-directional from source to target, but it can be made bi-directional. Only acts on changed records, so it is very fast even with linked servers on slower connection.
--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
Here is code to setup tables to test above:
--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

I think this answer deserves a little more love. It's simple, elegant and works. However, depending on the tables in question, it may be a little bit slow because the except clause is evaluating every column.
I suspect you can save a little bit of time by just joining on the primary key and the last modified date (if one exists).
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