代写代考 COMP9315 Final Exam

COMP9315 Final Exam

COMP9315 Final Exam

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The University of Wales

COMP9315 DBMS Implementation
Final Exam

DBMS Implementation

[Instructions] [Notes] [PostgreSQL] [C]

[Q1] [Q2] [Q3] [Q4] [Q5] [Q6] [Q7] [Q8]

Question 3 (6 marks)

Consider the following SQL statements to create three tables:

create table Students (
id integer primary key,
name text not null

create table Courses (
id integer primary key,
code char(8),
title text not null

create table Enrolments (
stude integer references Students(id),
course integer references Courses(id),
mark integer check (mark between 0 and 100),
grade char(2) check (grade in (‘FL’,’PS’,’CR’,’DN’,’HD’)),
primary key (stude,course)

Consider also that you insert 1000 tuples into each of the
Students and Courses tables, and insert
exactly 4 Enrolments tuples for each student.

The pg_class catalog table has a field reltuples
that indicates the total number of tuples stored in the pages of
the relation. This includes tuples that have been deleted, but
not yet vacuum’d.

For each parts (a), (b) and (c), what values will be produced
from the queries:

select count(*) from Enrolments;
select reltuples from pg_class where relname=’enrolments’;

after all the tuples are initially inserted (as above)

after the SQL statement
delete from Enrolments where stude = 1234567;

(but before any vaccuuming)

after the SQL statement delete from Enrolments;
(but before any vaccuuming)

if the SQL statement drop table Enrolments; is executed,
which of the following tables in the PostgreSQL catalog will be modified:

pg_aggregate, pg_attrdef, pg_attribute, pg_class, pg_collation,
pg_constraint, pg_conversion, pg_database, pg_depend, pg_enum,
pg_foreign_table, pg_index, pg_proc, pg_range, pg_rewrite,
pg_sequence, pg_transform, pg_tablespace, pg_trigger, pg_type

Note: incorrect table names are penalised; just writing them all scores zero.

The PostgreSQL catalog tables are described in detail in
Chapter 48
of the PostgreSQL documentation.

Instructions:

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End of Question

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