Unable to see list of tables in Oracle SQL Developer

List all users who have been assigned a particular role

-- Change 'DBA' to the required role
select * from dba_role_privs where granted_role = 'DBA'

List all roles given to a user

-- Change 'PHIL@ to the required user
select * from dba_role_privs where grantee = 'PHIL';

List all privileges given to a user

select
  lpad(' ', 2*level) || granted_role "User, his roles and privileges"
from
  (
  /* THE USERS */
    select 
      null     grantee, 
      username granted_role
    from 
      dba_users
    where
      username like upper('%&enter_username%')
  /* THE ROLES TO ROLES RELATIONS */ 
  union
    select 
      grantee,
      granted_role
    from
      dba_role_privs
  /* THE ROLES TO PRIVILEGE RELATIONS */ 
  union
    select
      grantee,
      privilege
    from
      dba_sys_privs
  )
start with grantee is null
connect by grantee = prior granted_role;

Note: Taken from http://www.adp-gmbh.ch/ora/misc/recursively_list_privilege.html

List which tables a certain role gives SELECT access to?

-- Change 'DBA' to the required role.
select * from role_tab_privs where role='DBA' and privilege = 'SELECT';

List all tables a user can SELECT from?

--Change 'PHIL' to the required user
select * from dba_tab_privs where GRANTEE ='PHIL' and privilege = 'SELECT';

List all users who can SELECT on a particular table (either through being given a relevant role or through a direct grant (ie grant select on atable to joe))? The result of this query should also show through which role the user has this access or whether it was a direct grant.

-- Change 'TABLENAME' below
select Grantee,'Granted Through Role' as Grant_Type, role, table_name
from role_tab_privs rtp, dba_role_privs drp
where rtp.role = drp.granted_role
and table_name = 'TABLENAME' 
union
select Grantee,'Direct Grant' as Grant_type, null as role, table_name
from dba_tab_privs
where table_name = 'TABLENAME' ;

The data dictionary will only show what it can.

Users can design their schema with or without referential integrity defined in the actual database.

When you import a data dictionary, using SQL Developer, to a new or existing relational data model, the foreign key constraints will be shown by default - if they are there to begin with.

Now, specific to the tool, it CAN attemp to infer any relationships. It does this by looking for common column names sprinkled around your tables, like an 'XYZ_ID' column, that happens to be a PRIMARY KEY in a driving table.

I have step-by-step instructions for this here, on my blog.