Primary & foreign keys and the tables & columns they reference.

Referenced primary keys
Simple query that lists all primary keys and the tables & columns they use. Adjust the where clause to your needs.

Hierarchy of primary & foreign keys
A more complex query:
This will travel the hierarchy of foreign keys for a given table and column and return columns from child and grandchild, and all descendant tables.
It uses sub-queries to add r_table_name and r_column_name to user_constraints, and then uses them to connect rows.
Adjust the where clause to your needs.

To get this to work, either run these queries as sys/system, change the quries to use the user_% or all_% views instead of sys_% views, or give the user these 2 privileges: grant select on dba_constraints to tedstruik; grant select on dba_cons_columns to tedstruik;
You can find the original queries here; I did change them quite a bit to make them more legible and to use the dba_% views:
http://stackoverflow.com/questions/1729996/list-of-foreign-keys-and-the-tables-they-reference

Region

Identification
	Sequence	10
	Title	Referenced primary keys
	Type	Report
Source
	Source Type	Report
	Region Source	select c.owner ,c.table_name ,a.column_name ,a.constraint_name ,c.delete_rule ,c.status ,a_r.owner as r_owner ,a_r.table_name as r_table_name ,a_r.column_name as r_column_name from user_cons_columns a join user_constraints c on c.constraint_name = a.constraint_name left join user_cons_columns a_r on a_r.constraint_name = c.r_constraint_name where c.constraint_type = 'R' -- # set your filters here and ( (c.owner = 'TEDSTRUIK' and c.table_name in ('EMP', 'DEPT')) or (a_r.owner = 'TEDSTRUIK' and a_r.table_name in ('EMP', 'DEPT')) ) order by a.owner ,a.table_name ,a.column_name ,a.constraint_name

Region

Identification
	Sequence	20
	Title	Hierarchy of primary & foreign keys
	Type	Interactive Report
Source
	Source Type	Interactive Report
	Region Source	select distinct owner ,table_name ,constraint_type ,constraint_name ,position ,column_name ,r_owner ,r_table_name ,r_column_name from (select uc.owner ,uc.table_name ,uc.constraint_name ,cols.column_name ,cols_r.owner as r_owner ,cols_r.table_name as r_table_name ,cols_r.column_name as r_column_name ,cols.position ,uc.constraint_type from dba_constraints uc join dba_cons_columns cols on cols.constraint_name = uc.constraint_name left join dba_cons_columns cols_r on cols_r.constraint_name = uc.r_constraint_name where uc.constraint_type not in ('C', 'U') -- C = check constraint, P = primary key, R = Foreign key, U = unique key and uc.table_name not like 'BIN$%' -- exclude system "tables" -- # set your filters here and uc.owner = 'TEDSTRUIK' ) -- # and set the rest of your filters here -- start with table_name = 'EMP' -- and column_name = 'EMPNO' connect by nocycle prior owner = r_owner and prior table_name = r_table_name and prior column_name = r_column_name order by owner ,table_name ,constraint_type ,constraint_name ,position