CREATE FUNCTION identityID()
RETURNS char(11)
AS
BEGIN
    RETURN(SELECT 'KT'+RIGHT(1000000001+ISNULL(RIGHT(MAX(KT),9),0),9) FROM Table_2 WITH(XLOCK,PAGLOCK))
END
GO


CREATE TABLE Table_2(
KT char(11) PRIMARY KEY DEFAULT dbo.identityID(),
Number int)


insert into Table_2 (Number)values(2)
insert into Table_2 (Number)values(3)
insert into Table_2 (Number)values(4)
insert into Table_2 (Number)values(5)
insert into Table_2 (Number)values(6)