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)
zipcodes(zip,city)
orders(ono,cno,eno,received,shipped)
odetails(ono,pno,qty)
The attribute names are self-explanatory. "qoh" stands for quantity on
hand. Specify and execute the following queries using Datalog and SQL:
- (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 only
from employees living in the city of Wichita.
- (e) Retrieve the names of customers who have ordered all parts
costing less than $20.00.
- (f) Retrieve the names of customers who have not placed a single order.
- (g) Retrieve the names of customers who have placed exactly two orders.