I am looking for the correct syntax and way to do the following directly from SQL: insert or update (if data already exists inside) `TableMain` from data contained in `TableA` with both having same composite primary key.

Both tables are defined as :

```
CREATE TABLE TableA (
[TID0] [int] NOT NULL,
[TID1] [int] NOT NULL,
[language] [nvarchar](2) NOT NULL,
[TID2] [nvarchar](200) NOT NULL,
[text] [nvarchar](max) NULL,
[updatedOn] [datetime] NOT NULL  DEFAULT (getdate())
PRIMARY KEY (
    [TID0],
    [TID1],
    [language],
    [TID2],
)
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

```

`TableA` will be periodically deleted and filled.

`TableMain` as the same definition but will contain many more rows of data and what I need is to insert never seen values from `TableA` into `TableMain`, and update already existing rows.

I used to do this kind of insert but I do not know how to handle update and composite primary keys :

```
INSERT INTO TableMain 
    SELECT * FROM TableA

```

EDIT : i am using **SQL Server 9.00.5000**

EDIT : another way inspired by MERGE and [mimick it](http://sqlserver-tips.blogspot.fr/2006/09/mimicking-merge-statement-in-sql.html)

```
DECLARE @updatedIDs TABLE(
    [TID0] [int],
    [TID1] [int],
    [language] [nvarchar](2),
    [TID2] [nvarchar](200),
                PRIMARY KEY ([TID0], [TID1], [language], [TID2])  -- as stated by Nikola Markovinović above, thanks
);

-- First update records 
update TableMain 
   set [text]      = source.[text], 
       [updatedOn] = source.[updatedOn] 
       OUTPUT
         inserted.[TID0]
         inserted.[TID1]
         inserted.[language]
         inserted.[TID2]
       INTO @updatedIDs
  from 
       TableMain AS main
       , TableA AS source 
  WHERE    
   TableMain.[TID0]         = source.[TID0] 
   and TableMain.[TID1]     = source.[TID1] 
   and TableMain.[language] = source.[language] 
   and TableMain.[TID2]     = source.[TID2] 

-- And then insert 

insert into TableMain
select *
  from TableA AS source 
 where not exists 
       ( 
      select 1
        from @updatedIDs AS i
       where i.[TID0]     = source.[TID0] 
         and i.[TID1]     = source.[TID1] 
         and i.[language] = source.[language] 
         and i.[TID2]     = source.[TID2] 
       )

```