Foreign key oracle

Foreign key on table oracle

SELECT c.OWNER, a.TABLE_NAME, a.COLUMN_NAME, a.CONSTRAINT_NAME, 
       c.R_OWNER AS REF_OWNER, cpk.TABLE_NAME AS REF_TABLE, 
       cpk.CONSTRAINT_NAME AS REF_PK
FROM ALL_CONS_COLUMNS a 
JOIN ALL_CONSTRAINTS c ON a.OWNER = c.OWNER
    AND a.CONSTRAINT_NAME = c.CONSTRAINT_NAME
 JOIN ALL_CONSTRAINTS cpk ON c.R_OWNER = cpk.OWNER
    AND c.R_CONSTRAINT_NAME = cpk.CONSTRAINT_NAME
WHERE c.CONSTRAINT_TYPE = 'R' AND c.TABLE_NAME= 'table_name';

Oracle foreign key reference table

SELECT cons.OWNER 			AS CHILD_OWNER,
       cons.TABLE_NAME 		AS CHILD_TABLE,
       cons.CONSTRAINT_NAME AS CONSTAINT_NAME,
       cons.CONSTRAINT_TYPE AS CONSTRAINT_TYPE,
       col.OWNER 			AS PARENT_OWNER,
       col.TABLE_NAME 		AS PARENT_TABLE,
       col.COLUMN_NAME 		AS COLUMN_NAME
FROM DBA_CONS_COLUMNS col, DBA_CONSTRAINTS cons
WHERE cons.R_OWNER = col.OWNER
  AND cons.R_CONSTRAINT_NAME = col.CONSTRAINT_NAME
  AND cons.TABLE_NAME = 'table_name';

Source: dba-oracle.com

Foreign key oracle

ALTER TABLE table_name
ADD CONSTRAINT constraint_name
   FOREIGN KEY (column1, column2, ... column_n)
   REFERENCES parent_table (column1, column2, ... column_n);

Example

ALTER TABLE products
ADD CONSTRAINT fk_supplier
  FOREIGN KEY (supplier_id)
  REFERENCES supplier(supplier_id);

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