Problem With MS SQL

[sibusiso]

HI

Can Any one help I am having a problem with SQL triggers.

I am having this table

create table TTest(
id bigint identity(100000 01,1),
UID varchar(10),
Fdesplayname varchar(50),
primary key(id,UID)
);

On my triger I want to say
FOR INSERT let the trigger take id and 'UID' and put it in field UID out put will look like 'UID1000001'

the triger I did look like

CREATE TRIGGER tr_Test
ON dbo.TTest
FOR INSERT
AS
BEGIN
SET NOCOUNT ON;
DECLARE @Num bigint
SET @Num = (SELECT id FROM inserted);
UPDATE TTest
SET UID = 'UID'+@Num
WHERE id = (SELECT id FROM inserted);
END

but it will only work if UID is no primary key

Can Any one help

Thanks