Mock Exam Flashcards
What does the HAVING clause do?
filters the rows (after aggregation)
What does the SELECT line do?
determines which columns appear
What does the FROM clause do?
determines which tables are searched
What does the GROUP BY clause do?
determines how aggregate functions are evaluated
What does the WHERE clause do?
filters the rows (before aggregation)
What should a composite key index do?
It should improve the performance of some SELECT queries.
Of the following options, which is Database Vendor Dependent:
- Physical Design
- The Data Dictionary
- Logical Design
- Normalisation
Physical Design
What is an important part of a database administrator’s role
Ensuring that the database is backed up regularly.
All tables must have a foreign key - True or False?
False
Foreign Keys ensure referential integrity - True or False?
True
What is the term for combining two relations based on values in one attribute in each relation being the same?
Equi-Join
The label at the “child” end of an optional, one-to-many relationship should be:
0..*
What is the stage of normalisation at which the following issue is addressed:
Eliminate partial key dependancies:
Second Normal Form
Select the true statement about the multiplicity label shown:
0..1
Select one:
a. The entity is mandatory. The corresponding foreign key cannot be null.
b. The entity is optional. The corresponding foreign key cannot be null.
c. This is not a valid multiplicity label.
d. The entity is optional. The corresponding foreign key may be null.
e. The entity is mandatory. The corresponding foreign key may be null.
The entity is optional. The corresponding foreign key may be null.
Each table should have exactly one Primary Key - True or False?
True
What is the term for the maximum number of entities that can participate in a relationship?
Cardinality
What does ‘Access Control’ allow a user to do?
allows user X to insert records into table T
What is an appropriate response to an SQL injection attack
Inspect program code to ensure that SQL statements cannot be compromised.
What part of SQL uses the ‘ON’ condition
JOIN
What is the mongodb function that corresponds most closely to an SQL SELECT statement with a GROUP BY clause.
aggregate
What is meant by Scalability in regards to NoSQL
NoSQL databases allow many machines to process a single query simultaneously.
Relational Databases are so called because…
a. It is important to maintain good relations.
b. The main data structure used is a relation.
c. The database manages relations between entities.
d. Only related data can be stored in these databases.
e. All implementations are related.
b. The main data structure used is a relation.
Using a transaction log reduces Database Performance - True or False?
True
Which property of transactions is guaranteed by the two-phase locking strategy?
Serialisability
What is the term for the conceptual separation of logical data from physically stored data?
Data Independence
What is the term for a lock taken out by a read-only transaction?
Shared
