query to get constraint between parent and child table

Question

I am new to oracle, I am working on tables where I need to fetch constraints between 2 tables and send the values as another input.

Table 1
  |_ Column1_pk
  |_ Column2 (foreign key to Table 2) 

Table 2
  |_column2 

So I want to fetch primary key of table1 and column which have the relation between 2 tables

Answer 1

You need to query the dictionary views USER_CONSTRAINTS and USER_CONS_COLUMNS . For example:

Table DEPT has a primary key, and table EMP has a foreign key pointing to DEPT . First we find the constraint name, and then the column(s), of the primary key of DEPT . Then, with the constraint name in hand, we find the constraint name, and then the column(s), for the foreign key of EMP .

select table_name, constraint_name, constraint_type
from   user_constraints
where  table_name      = 'DEPT'
  and  constraint_type = 'P'
;

TABLE_NAME  CONSTRAINT_NAME  CONSTRAINT_TYPE
----------  ---------------  ---------------
DEPT        PK_DEPT          P

select constraint_name, table_name, column_name, position
from   user_cons_columns
where  constraint_name = 'PK_DEPT'
;

CONSTRAINT_NAME  TABLE_NAME  COLUMN_NAME  POSITION
---------------  ----------  -----------  --------
PK_DEPT          DEPT        DEPTNO              1

and then

select table_name, constraint_name, constraint_type
from   user_constraints
where  table_name        = 'EMP'
  and  r_constraint_name = 'PK_DEPT'
;

TABLE_NAME  CONSTRAINT_NAME  CONSTRAINT_TYPE
----------  ---------------  ---------------
EMP         FK_DEPTNO        R

select constraint_name, table_name, column_name, position
from   user_cons_columns
where  constraint_name = 'FK_DEPTNO'
;

CONSTRAINT_NAME  TABLE_NAME  COLUMN_NAME  POSITION
---------------  ----------  -----------  --------
FK_DEPTNO        EMP         DEPTNO              1