Consider the following MAILORDER relational schema describing the data for a mail-order company.
PARTS(Pno, Pname, Qoh, Price, Olevel)
CUSTOMERS(Cno, Cname, Street, Zip, Phone)
EMPLOYEES(Eno, Ename, Zip, Hdate)
ORDERS(Ono, Cno, Eno, Received, Shipped)
ODETAILS(Ono, Pno, Qty)
Qoh stands for quantity on hand: the other attribute names are selfexplanatory.
Specify and execute the following queries on the MAILORDER database schema.
a. Retrieve the names of parts that cost less than $20.00.
b. Retrieve the names and cities of employees who have taken orders for
parts costing more than $50.00.
c. Retrieve the pairs of customer number values of customers who live in
the same ZIP Code.
d. Retrieve the names of customers who have ordered parts from employees
living in Wichita.
e. Retrieve the names of customers who have ordered parts costing less than
f. Retrieve the names of customers who have not placed an order.
g. Retrieve the names of customers who have placed exactly two orders.