how to function parameter take value automatically in sql server

i have create a table

infobool (
   book_id int identity(1,1) primary key,
   bid varchar(20),bname varchar(50)
 )

now i want use a function

dbo.book_id(@a int)
returns varchar(20)
as
begain
return 'bkid00'+convert(varchar(10),@a)
end

now how this function take automatica开发者_运维知识库lly value from book_id column

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It looks like you are just trying to prepend a value to your book_id column? You can achieve that without a function, try something like this:

SELECT 'bkid00' + CONVERT(VARCHAR(10, book_id), bid
FROM infobool