PL/SQL Cursors - Retrieving data from multiple tables - sql

Question

I need to input a product code as a parameter that will retrieve said product and other information. I require more info than I have provided, I've started small scale to attempt to debug any errors early, but I cannot see why the code below doesn't work. I'm using SQLPlus, any help would be greatly appreciated.
CREATE OR REPLACE PROCEDURE product_info(PRODUCT_NO IN CHAR)
AS
v_product PRODUCTS%ROWTYPE;
v_suborders SUBORDERS.ORDER_NO%TYPE;
CURSOR cur_products IS
SELECT p.name, p.prod_id, p.description, p.unit_price, s.order_no
FROM PRODUCTS P, SUBORDERS S
WHERE p.prod_id = product_no;
BEGIN
OPEN cur_products;
LOOP
FETCH cur_products INTO v_product, v_suborders;
DBMS_OUTPUT.PUT_LINE('Product Code: ' || v_product.prod_id
|| ' Name: ' || v_product.name
|| ' Description: ' || v_product.description
|| ' Price: ' || v_product.unit_price
|| ' Order: ' || v_suborders);
END LOOP;
EXCEPTION
WHEN no_data_found THEN
DBMS_OUTPUT.PUT_LINE ('Product number does not exist');
WHEN OTHERS THEN DBMS_OUTPUT.PUT_LINE ('Operation failed ' || 'SQLCODE: ' || SQLCODE);
ROLLBACK;
END;
/

Answer 1

When we fetch into a variable its structure must match the projection of the query we're fetching. Or if we're fetching into multiple variables we need one variable per column in the projection. Your code doesn't do either.
The simplest solution is to use your cursor to define the variable, like this:
CURSOR cur_products IS
SELECT p.name, p.prod_id, p.description, p.unit_price, s.order_no
FROM PRODUCTS P, SUBORDERS S
WHERE p.prod_id = product_no;
v_rec cur_products%ROWTYPE;
BEGIN
OPEN cur_products;
LOOP
FETCH cur_products INTO v_rec;
...
An alternate solution is to use an implicit cursor. You could rewrite your code like this:
CREATE OR REPLACE PROCEDURE product_info(PRODUCT_NO IN CHAR)
AS
BEGIN
for v_rec in (SELECT p.name, p.prod_id, p.description, p.unit_price, s.order_no
FROM PRODUCTS P, SUBORDERS S
WHERE p.prod_id = product_no )
LOOP
DBMS_OUTPUT.PUT_LINE('Product Code: ' || v_rec.prod_id
|| ' Name: ' || v_rec.name
|| ' Description: ' || v_rec.description
|| ' Price: ' || v_rec.unit_price
|| ' Order: ' || v_rec.odrer_no);
END LOOP;
EXCEPTION
WHEN no_data_found THEN
DBMS_OUTPUT.PUT_LINE ('Product number does not exist');
WHEN OTHERS THEN DBMS_OUTPUT.PUT_LINE ('Operation failed ' || 'SQLCODE: ' || SQLCODE);
ROLLBACK;
END;
/
Incidentally, you query doesn't have a join between PRODUCTS and SUBORDERS so your result set will be a product (cross-join) or all the records in both tables. Almost certainly you don't want that.
Also, it is bad practice not to re-raise an exception in the exception handler (apart from some edge cases). It doesn't matter in a piece of toy code like this, but don't fall into bad habits.