Defining Foreign Key in Unary Relationship <p>I have the table assignment which should have two FK - ManagerID &amp; ManagerProjID</p> <pre><code>CREATE TABLE Assignment ( RescID NUMBER (8) NOT NULL , RProjID NUMBER (4) NOT NULL , AssignRole VARCHAR2(100) , ManagerID NUMBER (8) , ManagerProjID NUMBER (4), CONSTRAINT Assignment_PK PRIMARY KEY ( RescID, RProjID) ) ; </code></pre> <p>When I try running the command </p> <pre><code>ALTER TABLE Assignment ADD CONSTRAINT Assignment_Manager_FK FOREIGN KEY ( MANAGERID ) REFERENCES Assignment ( MANAGERID ) ; </code></pre> <p>I am getting an error of no matching unique or primary key for this column-list. </p>