Questions
1. The following relations keep track of airline flight information:
Flights(flno: integer, from: string, to: string, distance: integer, departs:
time,
arrives: time, price: integer)
Aircraft(aid: integer, aname: string, cruisingrange: integer)
Certified(eid: integer, aid: integer)
Employees(eid: integer, ename: string, salary: integer)
Note that the Employees relation describes pilots and other kinds of employees
aswell; every pilot is certified for some aircraft, and only pilots are certified to
fly.Write each of the following queries in SQL.
a. Find the names of aircraft such that all pilots certified to operate them earn
more than $80,000.
b. For each pilot who is certified for more than three aircraft, find the eid and the
maximum cruisingrange of the aircraft for which she or he is certified.
c. Find the names of pilots whose salary is less than the price of the cheapest
route from Los Angeles to Honolulu.
d. For all aircraft with cruisingrange over 1000 miles, find the name of the
aircraft and the average salary of all pilots certified for this aircraft.
e. Find the names of pilots certified for some Boeing aircraft.
f. Find the aids of all aircraft that can be used on routes from Los Angeles to
Chicago.
g. Identify the routes that can be piloted by every pilot who makes more than
$100,000.
h. Print the enames of pilots who can operate planes with cruisingrange greater
than 3000 miles but are not certified on any Boeing aircraft.
i. A customer wants to travel from Madison to New York with no more than two
changes of flight. List the choice of departure times from Madison if the
customer wants to arrive in New York by 6 p.m.
j. Compute the difference between the average salary of a pilot and the average
salary of all employees (including pilots).
k. Print the name and salary of every nonpilot whose salary is more than the
average salary for pilots.
l. Print the names of employees who are certified only on aircrafts with cruising
range longer than 1000 miles.
m. Print the names of employees who are certified only on aircrafts with cruising
range longer than 1000 miles, but on at least two such aircrafts.
n. Print the names of employees who are certified only on aircrafts with cruising
range longer than 1000 miles and who are certified on some Boeing aircraft.
Ans:
a. SELECT DISTINCT A.aname
FROM Aircraft A
WHERE A.Aid IN (SELECT C.aid
FROM Certified C, Employees E
WHERE C.eid = E.eid AND
NOT EXISTS ( SELECT *
FROM Employees E1
WHERE E1.eid = E.eid AND E1.salary < 80000 ))
b. SELECT C.eid, MAX (A.cruisingrange)
FROM Certified C, Aircraft A
WHERE C.aid = A.aid
GROUP BY C.eid
HAVING COUNT (*) > 3
c. SELECT DISTINCT E.ename
FROM Employees E
WHERE E.salary < ( SELECT MIN (F.price)
FROM Flights F
WHERE F.from = ‘Los Angeles’ AND F.to = ‘Honolulu’ )
d. Observe that aid is the key for Aircraft, but the question asks for aircraft names; we deal with this
complication by using an intermediate relation Temp:
SELECT Temp.name, Temp.AvgSalary
FROM ( SELECT A.aid, A.aname AS name, AVG (E.salary) AS AvgSalary
FROM Aircraft A, Certified C, Employees E
WHERE A.aid = C.aid AND C.eid = E.eid AND A.cruisingrange > 1000
GROUP BY A.aid, A.aname ) AS Temp
e. SELECT DISTINCT E.ename
FROM Employees E, Certified C, Aircraft A
WHERE E.eid = C.eid AND C.aid = A.aid AND A.aname LIKE ‘Boeing%’
f. SELECT A.aid
FROM Aircraft A
WHERE A.cruisingrange > ( SELECT MIN (F.distance)
FROM Flights F
WHERE F.from = ‘Los Angeles’ AND F.to = ‘Chicago’ )
g. SELECT DISTINCT F.from, F.to
FROM Flights F
WHERE NOT EXISTS ( SELECT *
FROM Employees E
WHERE E.salary > 100000
AND
NOT EXISTS (SELECT *
FROM Aircraft A, Certified C
WHERE A.cruisingrange > F.distance AND
E.eid = C.eid AND A.aid = C.aid) )
h. SELECT DISTINCT E.ename
FROM Employees E
WHERE E.eid IN ( ( SELECT C.eid
FROM Certified C
WHERE EXISTS ( SELECT A.aid
FROM Aircraft A
WHERE A.aid = C.aid
AND A.cruisingrange > 3000 )
AND
NOT EXISTS ( SELECT A1.aid
FROM Aircraft A1
WHERE A1.aid = C.aid
AND A1.aname LIKE ‘Boeing%’ ))
i. SELECT F.departs
FROM Flights F
WHERE F.flno IN ( ( SELECT F0.flno
FROM Flights F0
WHERE F0.from = ‘Madison’ AND F0.to = ‘New York’
AND F0.arrives < ‘18:00’ )
UNION
( SELECT F0.flno
FROM Flights F0, Flights F1
WHERE F0.from = ‘Madison’ AND F0.to <> ‘New York’
AND F0.to = F1.from AND F1.to = ‘New York’
AND F1.departs > F0.arrives
AND F1.arrives < ‘18:00’ )
UNION
( SELECT F0.flno
FROM Flights F0, Flights F1, Flights F2
WHERE F0.from = ‘Madison’
AND F0.to = F1.from
AND F1.to = F2.from
AND F2.to = ‘New York’
AND F0.to <> ‘New York’
AND F1.to <> ‘New York’
AND F1.departs > F0.arrives
AND F2.departs > F1.arrives
AND F2.arrives < ‘18:00’ ))
j. SELECT Temp1.avg - Temp2.avg
FROM (SELECT AVG (E.salary) AS avg
FROM Employees E
WHERE E.eid IN (SELECT DISTINCT C.eid
FROM Certified C )) AS Temp1,
(SELECT AVG (E1.salary) AS avg
FROM Employees E1 ) AS Temp2
k. SELECT E.ename, E.salary
FROM Employees E
WHERE E.eid NOT IN ( SELECT DISTINCT C.eid
FROM Certified C )
AND E.salary > ( SELECT AVG (E1.salary)
FROM Employees E1
WHERE E1.eid IN
( SELECT DISTINCT C1.eid
FROM Certified C1 ) )
l. SELECT E.ename
FROM Employees E, Certified C, Aircraft A
WHERE C.aid = A.aid AND E.eid = C.eid
GROUP BY E.eid, E.ename
HAVING EVERY (A.cruisingrange > 1000)
m. SELECT E.ename
FROM Employees E, Certified C, Aircraft A
WHERE C.aid = A.aid AND E.eid = C.eid
GROUP BY E.eid, E.ename
HAVING EVERY (A.cruisingrange > 1000) AND COUNT (*) > 1
n. SELECT E.ename
FROM Employees E, Certified C, Aircraft A
WHERE C.aid = A.aid AND E.eid = C.eid
GROUP BY E.eid, E.ename
HAVING EVERY (A.cruisingrange > 1000) AND ANY (A.aname = ’Boeing’)
2. Consider the following relational schema. An employee can work in more than
one department; the pct_time filed of the Works relation shows the percentage of
time that a given employee works in a given department.
Emp(eid: integer, ename: string, age: integer, salary: real)
Works(eid: integer, did: integer, pct_time: integer)
Dept(did: integer, dname: string, budget: real, managerid: integer)
Write the following queries in SQL:
a. Print the names and ages of each employee who works in both the Hardware
department and the Software department.
b. For each department with more than 20 full-time-equivalent employees (i.e.,
where the part-time and full-time employees add up to at least that many fulltime employees), print the did together with the number of employees that
work in that department.
c. Print the name of each employee whose salary exceeds the budget of all of the
departments that he or she works in.
d. Find the managerids of managers who manage only departments with budgets
greater than $1 million.
e. Find the enames of managers who manage the departments with the largest
budgets.
f. If a manager manages more than one department, he or she controls the sum
of all the budgets for those departments. Find the managerids of managers
who control more than $5 million.
g. Find the managerids of managers who control the largest amounts.
h. Find the enames of managers who manage only departments with budgets
larger than $1 million, but at least one department with budget less than $5
million.
Ans:
a. SELECT E.ename, E.age
FROM Emp E, Works W1, Works W2, Dept D1, Dept D2
WHERE E.eid = W1.eid AND W1.did = D1.did AND D1.dname = ‘Hardware’ AND
E.eid = W2.eid AND W2.did = D2.did AND D2.dname = ‘Software’
b. SELECT W.did, COUNT (W.eid)
FROM Works W
GROUP BY W.did
HAVING 2000 < ( SELECT SUM (W1.pct time)
FROM Works W1
WHERE W1.did = W.did )

c. SELECT E.ename
FROM Emp E
WHERE E.salary > ALL (SELECT D.budget
FROM Dept D, Works W
WHERE E.eid = W.eid AND D.did = W.did)
d. SELECT DISTINCT D.managerid
FROM Dept D
WHERE 1000000 < ALL (SELECT D2.budget
FROM Dept D2
WHERE D2.managerid = D.managerid )
e. SELECT E.ename
FROM Emp E
WHERE E.eid IN (SELECT D.managerid
FROM Dept D
WHERE D.budget = (SELECT MAX (D2.budget)
FROM Dept D2))
f. SELECT D.managerid
FROM Dept D
WHERE 5000000 < (SELECT SUM (D2.budget)
FROM Dept D2
WHERE D2.managerid = D.managerid )
g. SELECT DISTINCT tempD.managerid
FROM (SELECT DISTINCT D.managerid, SUM (D.budget) AS tempBudget
FROM Dept D
GROUP BY D.managerid ) AS tempD
WHERE tempD.tempBudget = (SELECT MAX (tempD.tempBudget)
FROM tempD)
h. SELECT E.ename
FROM Emp E, Dept D
WHERE E.eid = D.managerid GROUP BY E.Eid, E.ename
HAVING EVERY (D.budget > 1000000) AND ANY (D.budget < 5000000)