/********************************
查询表之间的主外键关系
********************************/
Select b.table_name 主键表名,
           b.column_name 主键列名,
           a.table_name 外键表名,
           a.column_name 外键列名
From (Select a.constraint_name,
                       b.table_name,
                       b.column_name,
                       a.r_constraint_name
          From user_constraints a, user_cons_columns b
         Where a.constraint_type = 'R'
           And a.constraint_name = b.constraint_name) a,
       (Select Distinct a.r_constraint_name, b.table_name, b.column_name
          From user_constraints a, user_cons_columns b
         Where a.constraint_type = 'R'
           And a.r_constraint_name = b.constraint_name) b
Where a.r_constraint_name = b.r_constraint_name