check size of a database

select (select 'Space_GIVEN_to_DB' from dual) as Note,

round(sum(d.bytes)/1024/1024/1024 + (sum(t.bytes)/1024/1024/1024),2) as Size_in_GB  

from

v$datafile d,

v$tempfile t

where

d.file#=t.file#(+)

group by 1

union

select

(select 'Space_USED_by_DB' from dual) as Note,

round(sum(size_in_bytes)/1024/1024/1024,2) Size_in_GB

from

(select

     tablespace_name,

     sum(bytes) size_in_bytes

  from

     dba_segments

  group by

     tablespace_name)

group by 1

order by 2 desc;