I am unable to create the Foreign key

Question

Hi,
I need to create the Foreign key which reffered to composite primary key.
the following table structure
Parent table
DIVISION, PROJECT_NUMBER, COMPETITION_PROJECT_NUMBER, COMPETITIVE_STMT_TYPE, SEQUENCE, CATEGORY, STATEMENT, USER_ID, RECORD_MODIFICATION_DATE
Here composite primary key columns(DIVISION, PROJECT_NUMBER, COMPETITION_PROJECT_NUMBER, COMPETITIVE_STMT_TYPE, SEQUENCE)
Child Table
DIVISION          VARCHAR2 (4)          
PROJECT_NUMBER          NUMBER (10)COMPETITION_PROJECT_NUMBER     NUMBER (10)          
COMPETITIVE_STMT_TYPE          VARCHAR2 (2)          
SEQUENCE     NUMBER (2)          
CATEGORY          VARCHAR2 (100)     
STATEMENT     LONG          
USER_ID     VARCHAR2 (100)          
RECORD_MODIFICATION_DATE     DATE     
ALTER TABLE COMPETITION_STMT ADD (CONSTRAINT COMPET_STMT_FK_PROJ_NUM foreign key
          (PROJECT_NUMBER) REFERENCES PROD_COMPET_XREF (PROJECT_NUMBER));
when i am trying to create foreign key i got this error
ORA-02270: no matching unique or primary key for this column-list
this is production issue Please help me.
Thanks in advance
Regards
Kumar.s

Answer 1

ALTER TABLE PROD_COMPET_XREF ADD (
CONSTRAINT PROD_COMP_XREF_PK_DPNCPNCT
PRIMARY KEY
(COMPETITION_PROJECT_NUMBER, PROJECT_NUMBER, DIVISION, PRODUCT_LOC_INDICATOR)
When you create a foreign key, it must reference a unique or primary key. The primary or Unique key must consist ONLY of those columns upon which the Primary key is based.
You must Alter the table and add a Unique key if you want to keep your compsite primary key constraint. The Unique key must be for only the column that your foreign key references. Then try to recreate your foreign key.
I doubt you will be able to add a foreign key because I suspect you might have multiple rows with the same value for this column based on your composite key; however, if you only intend for the project number to be listed only once and to be unique for each row, then the unique key may work or you may want to revist your primary key on this table. Perhaps you don't need it to be a composite PK???
If you can't work around that, one thing you can do is build a table based just on PROJECT_NUMBER that contains details about the project number and have other tables reference that. That is, if you have multiple rows with the same project number in that table. You may already have one? Perhaps you can build your foreign key to reference that?