I keep getting MySQL error #1054, when trying to perform this update query:
UPDATE MASTER_USER_PROFILE, TRAN_USER_BRANCH
WHERE MASTER_USER_PROFILE.USER_ID = TRAN_USER_BRANCH.USER_ID
AND TRAN_USER_BRANCH.BRANCH_ID = 17
Unknown column 'y' in 'field list'
Try using different quotes for "y" as the identifier quote character is the backtick (“`”). Otherwise MySQL "thinks" that you point to a column named "y".
See also MySQL 5 Documentation