Fundamentals of databases

Question 1

Data model

Answer 1

An abstract model for organising data and its relationship to real world entities.

Question 2

Entity-relationship modelling

Answer 2

A method of abstractly describing that data tabes and the relationships between them visually. They can be used to reduce redundancy and construct a relational database.

Question 3

Attribute

Answer 3

A characteristic specification that defines a property or feature about an entity stored in a database.

Question 4

Composite primary key

Answer 4

A primary key made up from two or more other keys.

Question 5

Foreign key

Answer 5

A linking attribute that joins two tables in a relational database by being a primary key in one and a foreign key in the other.

Question 6

Primary key

Answer 6

A unique identifier that identifies each record in a table.

Question 7

Relational databases

Answer 7

A database where separate tables are made for each entity, and relationships between entities are represented by foreign keys.

Question 8

First Normal Form (1NF)

Answer 8

A table with no repeating attributes. The intersection of each record and attribute produces exactly one value.

Question 9

Normalisation

Answer 9

The formal process of optimally designing data tables by reducing data redundancy and repetition by connecting them into normal forms.

Question 10

Second Normal Form (2NF)

Answer 10

A table in 1NF that has data that repeats across multiple records removed and put into a new table with appropriate relationships (no partial dependancies).

Question 11

Third Normal Form (3NF)

Answer 11

A table in 2NF where all attributes that are not the primary key are fully dependant on the primary key (no non-key dependancies).

Question 12

SQL

Answer 12

A language for relational database management and manipulation.

Question 13

Client server database

Answer 13

A system that provides simultaneous access to the database for multiple clients.

Question 14

Commitment ordering

Answer 14

A type of timestamp ordering that also takes into consideration that precedence of each transaction over other simultaneous transactions.

Question 15

Integrity

Answer 15

The idea of keeping a database consistent by ensuring that any changes made to data or relationships associated with a table are accounted for in all the linked tables.

Question 16

Record locks

Answer 16

A technique used to prevent simultaneous access to data in a database by locking a record when it is being edited or updated. Otherwise, inconsistencies may arise in the database.

Question 17

Serialisation

Answer 17

A technique used to preserve integrity by only allowing one transaction to be processed at a time on a client server database.

Question 18

Timestamp ordering

Answer 18

A technique to handle concurrent access by executing transactions from multiple users based on the value of their associated timestamp. Each transaction receives a timestamp whenever it begins.