ORA-02292: integrity constraint violated - child record found while creating procedures in ORACLE SQL Developer?

Question

I have written a procedure that has as input the CUSTOMER_ID. Then the procedure deletes the corresponding customer from the table CUSTOMERS.

CREATE OR REPlACE PROCEDURE DELETE_CUSTOMER 
(CUSTOMER_ID NUMBER) AS 
TOT_CUSTOMERS NUMBER;
BEGIN
    DELETE FROM CUSTOMERS
    WHERE CUSTOMERS.CUSTOMER_ID = DELETE_CUSTOMER.CUSTOMER_ID;
    TOT_CUSTOMERS := TOT_CUSTOMERS - 1;
    END;
/

I have to execute the procedure to delete customer with id 1.

EXECUTE DELETE_CUSTOMER(01);

When I do this, I get an error

Error starting at line : 120 in command -
BEGIN DELETE_CUSTOMER(01); END;
Error report -
ORA-02292: integrity constraint (TUG81959.ORDERS_FK_CUSTOMERS) violated - child record found
ORA-06512: at "TUG81959.DELETE_CUSTOMER", line 5
ORA-06512: at line 1
02292. 00000 - "integrity constraint (%s.%s) violated - child record found"
*Cause:    attempted to delete a parent key value that had a foreign
           dependency.
*Action:   delete dependencies first then parent or disable constraint.

I know this is because there is a foreign key for CUSTOMER_ID on the table ORDERS, which means the customer cannot be deleted because he has placed an order. How do I write the code so that I can first delete the corresponding ORDER_DETAILS and then delete the corresponding ORDERS so that I can finally be able to delete a record from CUSTOMERS?

I tried rewriting the code but I am just lost now:

CREATE OR REPlACE PROCEDURE DELETE_CUSTOMER 
(CUSTOMER_ID_IN NUMBER) AS 
TOT_CUSTOMERS NUMBER;
CURSOR C1 IS
DELETE FROM ORDERS
WHERE ORDERS.ORDER_ID = CUSTOMER_ID.ORDER_ID;
CURSOR C2 IS
DELETE FROM ORDER_DETAILS
WHERE ORDER_DETAILS.ORDER_ID = CUSTOMER_ID.ORDER_ID;
CURSOR C3 IS
DELETE FROM CUSTOMERS
WHERE CUSTOMERS.CUSTOMER_ID = DELETE_CUSTOMER.CUSTOMER_ID;
BEGIN
    OPEN C1;
    OPEN C2;
    OPEN C3;
    IF C1%FOUND AND C2%FOUND AND C3%FOUND
    THEN TOT_CUSTOMERS := TOT_CUSTOMERS - 1;
    END IF;
    CLOSE C1;
    CLOSE C2;
    CLOSE C3;
END;
/

Here are the tables for reference:

Solution

There are two ways to accomplish this :

You may use cascade on delete ( drop&create again ) :

---

   drop constraint order_details_fk_orders; 

   alter table order_details add constraint order_details_fk_orders 
   foreign key(order_id) references orders(order_id)  
   on delete cascade;

   delete orders where customer_id = &i_cust_id;

or

You may delete your detail records first :

---

with following procedure :

CREATE OR REPLACE PROCEDURE PR_DELETE_CUSTOMER(
                                                I_CUSTOMER_ID       orders.customer_id%type, 
                                                O_TOT_CUSTOMERS out number
                                              ) IS 
BEGIN
   delete order_details where order_id in ( select order_id from orders where customer_id = I_CUSTOMER_ID );
   delete orders where customer_id = I_CUSTOMER_ID;
   delete customers where customer_id = I_CUSTOMER_ID;
   select count(1) into O_TOT_CUSTOMERS from orders; 
END;

and then

 var v_tot_customers number;  
 execute pr_delete_customer(1,:v_tot_customers);  
 print v_tot_customers;