1.3.2 - Databases

Question 1

What is an Entity in a database?

Answer 1

An item of interest about which information is stored.

Question 2

What is a Relational Database?

Answer 2

A database that organizes data into tables, recognizing differences between entities.

Question 3

What is a Flat File database?

Answer 3

A database that consists of a single file, typically based around a single entity.

Question 4

How is a flat file typically described?

Answer 4

Entity(Attribute1, Attribute2, Attribute3…)

Question 5

What is a Primary Key?

Answer 5

A unique identifier for each record in a table.

Question 6

How is a Primary Key indicated in notation?

Answer 6

By underlining the attribute.

Question 7

What is a Foreign Key?

Answer 7

An attribute in one table that is the primary key in another, used to link tables.

Question 8

How is a Foreign Key indicated in notation?

Answer 8

Using an asterisk (*).

Question 9

What is a Secondary Key?

Answer 9

An attribute used to speed up searching and ordering, but is not unique.

Question 10

Why are Secondary Keys useful?

Answer 10

They allow searching on attributes users are likely to know (e.g., surname) rather than a primary key.

Question 11

What are the three types of relationships in Entity Relationship Modelling?

Answer 11

One-to-one, One-to-many, Many-to-many.

Question 12

What is a One-to-one relationship?

Answer 12

Each entity is linked to only one other entity (e.g., husband and wife).

Question 13

What is a One-to-many relationship?

Answer 13

One entity can be linked to many others (e.g., a mother and her children).

Question 14

What is a Many-to-many relationship?

Answer 14

One entity can be linked to many others, and vice versa (e.g., students and courses).

Question 15

How is a One-to-one relationship shown in a diagram?

Answer 15

With a single line connecting the entities.

Question 16

How is a One-to-many relationship shown?

Answer 16

With a single line and a crow’s foot (branch) on the ‘many’ side.

Question 17

How is a Many-to-many relationship shown?

Answer 17

With a crow’s foot (branch) on both sides.

Question 18

What is Normalisation?

Answer 18

The process of designing a database to reduce redundancy and improve data integrity.

Question 19

What are the goals of Normalisation?

Answer 19

No redundancy, consistent data, easy record addition/removal, support for complex queries.

Question 20

What are the three normal forms?

Answer 20

First Normal Form (1NF), Second Normal Form (2NF), Third Normal Form (3NF).

Question 21

What is required for a table to be in First Normal Form (1NF)?

Answer 21

No attribute can contain more than a single value.

Question 22

What is required for a table to be in Second Normal Form (2NF)?

Answer 22

It must be in 1NF and have no partial dependencies (no attribute depends on only part of a composite key).

Question 23

What is required for a table to be in Third Normal Form (3NF)?

Answer 23

It must be in 2NF and have no non-key dependencies (attributes depend only on the primary key).

Question 24

What is Indexing?

Answer 24

A method to store the position of records ordered by an attribute for fast data access.

Question 25

What is the purpose of a Secondary Index?

Answer 25

To make searching and ordering faster on non-primary key attributes.

Question 26

What is Data Capturing?

Answer 26

The process of inputting data into a database.

Question 27

What is MICR and where is it used?

Answer 27

Magnetic Ink Character Recognition; used by banks to read details on cheques.

Question 28

What is OMR?

Answer 28

Optical Mark Recognition; used for reading multiple-choice answer sheets.

Question 29

What is OCR?

Answer 29

Optical Character Recognition; used for converting scanned text into machine-encoded text.

Question 30

What is Data Selection?

Answer 30

The process of choosing only relevant data that fits certain criteria.

Question 31

What is EDI?

Answer 31

Electronic Data Interchange; a method for computers to exchange data without human interaction.

Question 32

What does SQL stand for?

Answer 32

Structured Query Language.

Question 33

What type of language is SQL?

Answer 33

A declarative language.

Question 34

What does the SELECT statement do?

Answer 34

Specifies which columns (attributes) to retrieve from a table.

Question 35

What does the FROM statement do?

Answer 35

Specifies which table(s) to retrieve data from.

Question 36

What does the WHERE clause do?

Answer 36

Filters records based on specified conditions.

Question 37

What does the ORDER BY clause do?

Answer 37

Sorts the result set by a specified column(s).

Question 38

How do you sort in descending order?

Answer 38

Add the keyword DESC after the column name in ORDER BY.

Question 39

What does the JOIN operation do?

Answer 39

Combines rows from two or more tables based on a related column.

Question 40

What does the CREATE statement do?

Answer 40

Creates a new database or table.

Question 41

What does the ALTER statement do?

Answer 41

Adds, deletes, or modifies columns in an existing table.

Question 42

What does INSERT INTO do?

Answer 42

Adds a new record (row) to a table.

Question 43

What does UPDATE do?

Answer 43

Modifies existing records in a table.

Question 44

What does DELETE do?

Answer 44

Removes records from a table.

Question 45

What is Referential Integrity?

Answer 45

A property ensuring consistency; it prevents deletion of data that is referenced by other data.

Question 46

What is a Transaction?

Answer 46

A single operation or a logical unit of work on data.

Question 47

What does ACID stand for?

Answer 47

Atomicity, Consistency, Isolation, Durability.

Question 48

What is Atomicity?

Answer 48

A transaction must be processed completely or not at all.

Question 49

What is Consistency?

Answer 49

A transaction must maintain database rules and integrity.

Question 50

What is Isolation?

Answer 50

Concurrent transactions must not interfere with each other.

Question 51

What is Durability?

Answer 51

Once a transaction is committed, it remains so permanently.

Question 52

What is Record Locking?

Answer 52

Preventing simultaneous access to a record to prevent inconsistencies.

Question 53

What is a Deadlock?

Answer 53

A situation where two or more transactions are waiting for each other to release locks, causing a standstill.

Question 54

What is Redundancy in data management?

Answer 54

Having duplicate copies of data in physically separate locations for backup and recovery.