Query Select Oracle PLSQL Tutorial

SQL>
SQL> SELECT username, default_tablespace
  2  FROM dba_users
  3  where rownum < 50
  4  ORDER BY username desc;
USERNAME                       DEFAULT_TABLESPACE
------------------------------ ------------------------------
XDB                            SYSAUX
TSMSYS                         SYSTEM
SYSTEM                         SYSTEM
SYS                            SYSTEM
PLSQL                          USERS
OUTLN                          SYSTEM
MDSYS                          SYSTEM
RNTSOFT                         SYSTEM
HR                             USERS
FLOWS_FILES                    SYSAUX
FLOWS_020100                   SYSAUX
DIP                            SYSTEM
DBSNMP                         SYSAUX
CTXSYS                         SYSAUX
ANONYMOUS                      SYSAUX
15 rows selected.