Analytical Functions Oracle PLSQL Tutorial

SQL>
SQL> select owner, tablespace_name, sum(bytes)/(1024*1024) total_meg
  2  from dba_extents
  3  where rownum < 50
  4  group by owner,tablespace_name
  5  /
OWNER                          TABLESPACE_NAME                 TOTAL_MEG
------------------------------ ------------------------------ ----------
SYS                            SYSTEM                                  4
SQL>