Question

Instructions When writing a query, write the query in a way that it would work over all possible database instances and not just for the given example instance! Consider the following database schema and example instance for a cab management database. Customer caccount Name gender DOB userName 15243 Pam M 1924 Pfan 26267 John F 1932 Null 3152 Alice F 1940 Null Ride r id caccount daccount Date cost 1 15243 6433 1/4/2019 50 2 23152 6464 1/5/2019 200 3 31523 6464 1/6/2020 70 User userName Password Type Psmith 1234 Customer Dpla 3456A Driver Sclik S1234 Customer Schema: Driver daccount Name username car_id zip Code 6433 Paul Psmith 1 150525 7526 John Null 2 60544 6464 Carry Roche В 60522 Car Cid Type Seat 1 3 2 Van 6 3 Regular 3 Luxury Customer: (caccount. Name, gender, userName) Driver (daccount, Name, username, car_id, zip Code) Rides (r_id, caccount, daccountdate, cost), where the caccount and daccount are foreign keys for customer and driver Car (c_id, type, seat. ) User (username, password, type)

Please do Question 9 only with JUST the Alegbra in one expression, thanks. I know how sql works, just confused on how to write the expressions

Answer 1

Q9.

For the resultant query, we need to join the relation Customer and User.

The common attribute between the two is userName. Thus the join condition would be

Cutomer.userName = User.userName

Use projection operator to project only the Customer Name, user Name and password.

The query is

$\pi_{Customer.CutomerName, Customer.userName, User.Password}(Customer \bowtie_{Customer.userName = User.userName}USER)$

If you have any questions comment down and please? upvote thanks...