Mysql set algebra operations - mysql

Question

I have an unusally worded Question that even my lab professor wasnt 100% sure on what it wants, but does have some idea which ill bring up. The given question is "A query listed below must be implemented with set algebra operations: Find a code of all customers who ordered product Tofu or product Tunnbrod"
My Professor believes its asking for a UNION JOIN in which i have come up with the following:
SELECT CUSTOMER_CODE
FROM ORDERS
WHERE CUSTOMER_CODE = ORDER_ID
UNION ALL
SELECT PRODUCT_NAME
FROM ORDER_DETAIL
WHERE PRODUCT_NAME = 'Tunnbrod' AND ‘Tofu’;
This code acts like a List and just makes Tunnbrod a customer code, so im unsure of what i need to actually do. My professor did mention joing the or and and operands, in which i tried and failed to get the expected results.
below are the tables for reference
CREATE TABLE ORDERS
(
ORDER_ID DECIMAL(9) NOT NULL,
CUSTOMER_CODE VARCHAR(5) NOT NULL,
EMPLOYEE_ID DECIMAL(9) NOT NULL,
ORDER_DATE DATE NOT NULL,
REQUIRED_DATE DATE,
SHIPPED_DATE DATE,
SHIP_VIA VARCHAR(40),
FREIGHT DECIMAL(10,2) DEFAULT 0,
SHIP_NAME VARCHAR(40),
SHIP_ADDRESS VARCHAR(60),
SHIP_CITY VARCHAR(15),
SHIP_REGION VARCHAR(15),
SHIP_POSTAL_CODE VARCHAR(10),
SHIP_COUNTRY VARCHAR(15),
CONSTRAINT PK_ORDERS PRIMARY KEY (ORDER_ID),
CONSTRAINT FK_CUSTOMER_CODE FOREIGN KEY (CUSTOMER_CODE) REFERENCES CUSTOMER(CUSTOMER_CODE),
CONSTRAINT FK_EMPLOYEE_ID FOREIGN KEY (EMPLOYEE_ID) REFERENCES EMPLOYEE(EMPLOYEE_ID),
CONSTRAINT FK_SHIP_VIA FOREIGN KEY (SHIP_VIA) REFERENCES SHIPPER(COMPANY_NAME)
);
CREATE TABLE ORDER_DETAIL
(
ORDER_ID DECIMAL(9) NOT NULL,
PRODUCT_NAME VARCHAR(40) NOT NULL,
UNIT_PRICE DECIMAL(10,2) NOT NULL DEFAULT 0,
QUANTITY DECIMAL(9) NOT NULL DEFAULT 1 ,
DISCOUNT DECIMAL(4,2) NOT NULL DEFAULT 0,
CONSTRAINT PK_ORDER_DETAIL PRIMARY KEY (ORDER_ID, PRODUCT_NAME),
CONSTRAINT FK_ORDER_ID FOREIGN KEY (ORDER_ID) REFERENCES ORDERS (ORDER_ID),
CONSTRAINT FK_PRODUCT_NAME FOREIGN KEY (PRODUCT_NAME) REFERENCES PRODUCT (PRODUCT_NAME),
CONSTRAINT CK_ORDER_DETAIL_UNIT_PRICE CHECK (UNIT_PRICE >= 0),
CONSTRAINT CK_ORDER_DETAIL_QUANTITY CHECK (QUANTITY > 0),
CONSTRAINT CK_ORDER_DETAIL_DISCOUNT CHECK (DISCOUNT between 0 and 1)
);

Answer 1

This is a strangely formulated question to an otherwise simple thing:
Select * orders inner join order_details where PRODUCT_NAME = 'Tunnbrod' OR PRODUCT_NAME = ‘Tofu’
you can, of course, explicitly use UNION instead of OR:
Select * orders inner join order_details where PRODUCT_NAME = 'Tunnbrod'
UNION
Select * orders inner join order_details where PRODUCT_NAME = ‘Tofu’