Which of the following assertions captures the requirement that the total number of students enrolled in a course cannot be greater the course quota? (a) O create assertion check_quota check (not exists ( select * from Courses c join Enrolments e on (e.course = c.id) group by e.student having count (*) > c.quota ); (b) O create assertion check_quota check (not exists ( select * from (select c.id, count(student) as nstu, c.quota from Courses c join Enrolments e on (e.course = c.id) group by c.id, c.quota ) as x where x.nstu > x.quota ); (c) O create assertion check_quota check (not exists ( select * from Courses c where c.quota >= (select count(*) from Enrolments e where e.course = c.id) ); (d) O None of the above is correct
Which of the following assertions captures the requirement that the total number of students enrolled in a course cannot be greater the course quota? (a) O create assertion check_quota check (not exists ( select * from Courses c join Enrolments e on (e.course = c.id) group by e.student having count (*) > c.quota ); (b) O create assertion check_quota check (not exists ( select * from (select c.id, count(student) as nstu, c.quota from Courses c join Enrolments e on (e.course = c.id) group by c.id, c.quota ) as x where x.nstu > x.quota ); (c) O create assertion check_quota check (not exists ( select * from Courses c where c.quota >= (select count(*) from Enrolments e where e.course = c.id) ); (d) O None of the above is correct
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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Transcribed Image Text:Which of the following assertions captures the requirement that the total number of students enrolled in a course cannot be greater than
the course quota?
(a) O
create assertion check_quota
check (not exists (
select *
from
Courses c join Enrolments e on (e.course = c.id)
group by e.student
having count(*) > c.quota
);
(b) O
create assertion check_quota
check (not exists (
select *
from
(select c.id, count(student) as nstu, c.quota
from
Courses c join Enrolments e on (e.course = c.id)
group by c.id, c.quot
) as x
where
x.nstu > x.quota
);
(c) O
create assertion check_quota
check (not exists (
select *
from
Courses c
where
c.quota >= (select count (*) from Enrolments e where e.course = c.id)
);
(d) O
None of the above is correct
Transcribed Image Text:Consider the following SQL schema:
create table Courses (
id integer primary key,
code text,
title text,
quota integer check (quota between 1 and 9999),
...
);
create table Enrolments (
student integer references Students (id),
course integer references Courses(id),
...
);
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