Oracle Common SQL statement _oracle

1, see what users in the database?
Select username from all_users;
2. See which DBA users are in the database?
Select username from dba_users;
3. See what tables The current user owns?
Select table_name from User_tables;
4, Oracle New table space, establish user steps?
A, create a table space
Create tablespace blueskydb datafile ' D:\oracle\product\10.2.0\oradata\bluesky\blueskydb.dbf ' size 500m;
B, New user
Create user BlueSky identified by BlueSky;
C, user authorization
Grant resource, connect, recovery_catalog_owner to BlueSky;
Grant CREATE table to BlueSky;
Alter user BlueSky quota unlimited on blueskydb;
Alter user BlueSky default Tablespace blueskydb;
D, this is OK, use sqlplus or other tools to connect to try it!