Returns the file identification (ID) number for the given logical file name in the current database.
FILE_ID ( 'file_name' )
'file_name'
Is the name of the file for which to return the file ID. file_name is nchar(128).
smallint
file_name corresponds to the name column in sysfiles.
This example returns the file ID (1) for the master database.
USE master
SELECT FILE_ID('master')