Find DB Size Order by Schemas, Oracle

select
   sum(bytes)/1024/1024 as size_in_megabyte,
   segment_type, owner
from
   dba_segments
where
   OWNER in ('MEISPSN','MEISPAY','HRIS', 'NDMS')
and
  segment_type like 'TABLE'
group by
   segment_type, owner
order by owner;


ALL DB SIze in Megabytes

set lines 200
set pages 999
col "DBSize" format a10
col "Free" format a10
col "Used" format a10
select    round(sum(used.bytes) / 1024 / 1024  ) || ' MB' "DBSize"
,    round(sum(used.bytes) / 1024 / 1024  ) -
    round(free.p / 1024 / 1024 ) || ' MB' "Used"
,    round(free.p / 1024 / 1024 ) || ' MB' "Free"
from    (select    bytes
    from    v$datafile
    union    all
    select    bytes
    from     v$tempfile
    union     all
    select     bytes
    from     v$log) used
,    (select sum(bytes) as p
    from dba_free_space) free
group by free.p
/

ALL DB Size in GB

set lines 200
set pages 999
col "DBSize" format a10
col "Free" format a10
col "Used" format a10
select    round(sum(used.bytes) / 1024 / 1024 / 1024  ) || ' GB' "DBSize"
,    round(sum(used.bytes) / 1024 / 1024 / 1024  ) -
    round(free.p / 1024 / 1024 / 1024 ) || ' GB' "Used"
,    round(free.p / 1024 / 1024 / 1024 ) || ' GB' "Free"
from    (select    bytes
    from    v$datafile
    union    all
    select    bytes
    from     v$tempfile
    union     all
    select     bytes
    from     v$log) used
,    (select sum(bytes) as p
    from dba_free_space) free
group by free.p
/