SELECT a.tablespace_name, "Free, MB", "Total, MB" FROM

  (SELECT tablespace_name, ROUND(SUM(bytes)/1024/1024) AS "Total, MB" FROM dba_data_files GROUP BY tablespace_name

  UNION

  SELECT tablespace_name, ROUND(SUM(bytes)/1024/1024) AS "Total, MB" FROM dba_temp_files GROUP BY tablespace_name) a,

  (SELECT tablespace_name, ROUND(SUM(bytes)/1024/1024) AS "Free, MB" FROM dba_free_space GROUP BY tablespace_name) b

WHERE a.tablespace_name = b.tablespace_name (+)

ORDER BY a.tablespace_name;

SELECT a.tablespace_name, total_bytes/1024/1024 AS "Total, MB", used_mbytes AS "Used, MB",

  (total_bytes/1024/1024 - used_mbytes) AS "Free, MB" FROM

    (SELECT tablespace_name, SUM(bytes_used + bytes_free) AS total_bytes

      FROM v$temp_space_header GROUP BY tablespace_name) a,

    (SELECT tablespace_name, used_blocks*8/1024 AS used_mbytes FROM v$sort_segment) b

WHERE a.tablespace_name=b.tablespace_name;