Question

2. Queries. Consider the following schema for a relational database. The schema models which Uber drivers drive which passengers to which destination at what time DRIVER-[did, dname, rating, car typej with key {did) PASSENGER-po, pname, email) with key pno) TRIP-did, pno, time, dest with key [did, time and foreign keys [did]CDRIVER[did pnoCPASSENGER pno]

Answer 1

1) Query in Relational Algebra :

?_pname ?_{pno in (}?_pno?_{dest=Spookers ^ did=(}?_did?_{car_type=Trabant)) (PASSENGER XTRIP X DRIVER)}

_where ? represents select and ? represents conditionality

2) Query in safe domain relational caluculus :

Q_{Speakers,Trabant}= {pname? PASSENGER(pame) ? (pno=TRIP(pno,dest='Spookers' ^ did=DRIVER(did,CAR_type=Trabant))}

3) Query in SQL :

select pname from PASSENGER where pno in (select pno from TRIP where dest='Spookers' and did=(

select did from DRIVER where car_type='Trabant'))