Dataview, Contains returning multiple entries

Things I have tried

I’m trying to list data for a book with specific book_code “SU.TO” except that Contains is returning everything that contains “SU.TO” inclduing “CSU.TO”, I want to return just “SU.TO”, tried the this.file_name = book_code but it doesn’t work.

file_listing
table file.link, book_code, book_name where contains(book_code, this.file.name)

My file name contains a code that should match with the “book_code” as in:

file 1: SU.TO

book_code: SU.TO

file 2: CSU.TO

book_code: CSU.TO

What I’m trying to do