To: Nabil Khan 
On Mon, 4 Oct 1999

Subject: Syntax to Make Foreign Key

> Dear Sir,
>          I am a student who is looking for a help. My question is:
> I have two tables :
> ORDERS                                      PRODUCTS
> ------                                      ---------
> ORDER_NUM (PRIMARY KEY)                     MFR_ID (PRIMARY KEY)
> MFR                                         PRODUCT_ID(PRIMARY KEY
> PRODUCT                                     ......
> .......
> The products table have composite primary key which is mfr_id and 
> product_id.
> 
> I did the following statement to add a foreign key to the orders table :
> ALTER TABLE ORDERS
> ADD FOREIGN KEY (MFR, PRODUCT) REFERENCES PRODUCTS;
> 
> It did not let me do that and told me that parents key did not found.
> How do I add a foreign key to orders table to make it reference product 
> table putting in mind that mfr and mfr_id have the same datatype and product 
> and product_id have the same datatype. I dont know what I did wrong but it 
> wont let me do that. I am trying to connect these two table together. How do 
> I make a relation ship between two tables.
> Your help is appreciated .
> 
> Sincerely,
> 
> Nabil Khan
> 
Nabil,

Your syntax was very close, but you forgot to specify which columns in the
PRODUCT table to use. The correct syntax is:

ALTER TABLE ORDERS ADD (CONSTRAINT fk_ORDERS1
      FOREIGN KEY (MFR, PRODUCT)
      REFERENCES PRODUCTS (MFR_ID, PRODUCT_ID));

Best regards,

-Ari Kaplan
Independent Oracle DBA Consultant

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