title: ORA-02270: no matching unique or primary key for this column-list
body: <p>I have a table, and the structure is </p>
  
  <pre><code>CREATE TABLE  "COURSE_ACCREDITED" 
  ("COURSE_ID" VARCHAR2(50) NOT NULL ENABLE, 
  "ACCREDITATION_BODY_ID" VARCHAR2(50) NOT NULL ENABLE, 
  "DATE_OBTAINED" VARCHAR2(50), 
   PRIMARY KEY ("COURSE_ID", "ACCREDITATION_BODY_ID", "DATE_OBTAINED") ENABLE, 
   CONSTRAINT "COURSE_ACCREDITED_CON" FOREIGN KEY ("COURSE_ID")
    REFERENCES  "COURSE" ("COURSE_ID") ENABLE)
  </code></pre>
  
  <p>When I add a constrain </p>
  
  <pre><code>alter table "COURSE_ACCREDITED" add constraint
  "COURSE_ACCREDITED_CON2" foreign key ("ACCREDITATION_BODY_ID") references "COURSE_ACCREDITED"    ("ACCREDITATION_BODY_ID")
  </code></pre>
  
  <p>It appears  ORA-02270: no matching unique or primary key for this column-list</p>
  
  <p>What is the problem?</p>