Oracle : Table's constraints and their associated tables and constraints

def owner = &&1 
def tab = &&2 

ttitle -  center  'Table &owner..&tab Constraints'  skip 2 

col name format a22 heading 'Name' justify c 
col type format a5  heading 'Type' justify c 
col stat format a4  heading 'Stat' justify c 
col ref_tab format a20 heading 'Reference|Object' justify c 
col ref_con format a22 heading 'Reference|Constraint' justify c 

select 
  a.constraint_name name, 
  decode(a.constraint_type,'C','Check','R','FK','P','PK','U','Uniq', 
    'C','Check','*') type, 
  decode(a.status,'ENABLED','Y','DISABLED','N','*') stat, 
  b.owner||'.'||b.table_name ref_tab, 
  a.r_constraint_name ref_con 
from 
  dba_constraints a, 
  dba_constraints b 
where 
  a.owner = upper('&owner') and 
  a.table_name = upper('&tab') and 
  a.r_constraint_name = b.constraint_name (+) 
order by 
  1 
/ 

undef owner 
undef tab