SQL Statements › ALTER TABLE › Processing › Example 5

Example 5

Prevent the acceptance of orders from customers who do not pay their bills by ensuring that any order accepted comes from a customer whose name is on a "customers in good standing" list.

1. Table containing customers in good standing: PAYING_CUSTOMERS
2. Table to be protected: ORDERS
3. Columns on which a match is required:

   ORDERS.CUSTOMER_NAME to PAYING_CUSTOMERS.COMPANY_NAME

4. Constraint name: ORDERS_TO_PAYING_CUST_NAME

    EXEC SQL
         ALTER TABLE ORDERS ADD FOREIGN KEY
            (CUSTOMER_NAME) REFERENCES PAYING_CUSTOMERS(COMPANY_NAME)
            CONSTRAINT ORDERS_TO_PAYING_CUST_NAME
    END-EXEC