I have also tried joining the table to itself, but I have no idea where to go with that
SELECT a.FILE_NAME, a.BYTES, a.MAXBYTES
FROM DBA_DATA_FILES a, dba_data_files b
WHERE a.FILE_NAME = b.FILE_NAME
AND a.autoextensible = 'YES'
AND a.maxbytes-a.bytes < 2097152
order by bytes;