Databases

Question 1

What is a database?

Answer 1

A database is a large collection of data items and links between them, structured in a way that allows it to be accessed by a number of different application programs.

The term is also used loosely to describe any collection of data.

Question 2

What is a Database Table?

Answer 2

A table is the name for each group of similar data with rows for each instance of an entity and columns for each attribute.

Question 3

What is a Record?

Answer 3

“[A] Record is the basic unit of data stored in a data file. It is a collection of data items, which may be of different data types, all relating to the individual or object that the record describes and is treated as a unit for processing.”

A record is really a row of data from a database table.

Question 4

What is a key field?

Answer 4

“[A] Key is the field within a record used to identify the record.”

Question 4

What is a Field?

Answer 4

[A] Field is part of a record designed to hold a single data item of a specified type.

A record is really a column of data from a database table.

Question 5

What is a primary key?

Answer 5

A field that uniquely identifies an individual record in a table can be chosen as the Primary Key of the table.

Question 6

What is a composite key?

Answer 6

A composite key is one that consists of two or more fields

Question 7

What is a foreign key?

Answer 7

When the primary key from one table appears as a field in a second table, it is known as a Foreign Key of the second table.

Question 8

Explain how relationships are used in databases.

Answer 8

The way relationships are represented in a relational database involves the use of primary and foreign keys. If the primary key of one table appears as a foreign key in a second table, then we say that there is a relationship or a link between the two tables.

We can see which individual athletes are related to which individual events by cross referencing the values in the respective foreign and primary key fields

Question 9

Definition of a data type

Answer 9

“[A] data type is a formal description of the kind of data being stored or manipulated within a program or system, for example CHAR (N), REAL or DATE

Question 10

Explain the data type - CHAR(N)

Answer 10

CHAR(N) is string data type, whose values are constrained to have exactly N
characters. For example the following are all CHAR(4): “Fred”, “Fre ”, “Fr d”, “1234”.

Question 11

Explain the data type - TEXT

Answer 11

TEXT is a string data type, whose values may have a variable numer of characters.
For example: “Fred”, Fre”, “Fr”, “F”, “Fred12345”.

Question 12

Explain the data type - ENUM

Answer 12

ENUM is a string data type, whose values are constrained to be one of a list of
permitted values

Question 13

Explain the data type -INT

Answer 13

INT is a numeric data type that can store whole numbers – which may be either
positive or negative. For example: 0, 1, 2, -99.

Question 14

Explain the data type - REAL

Answer 14

REAL is a numeric data type that can store numbers with decimal places. For example:
1, 2.718, 3.141, -2.718, -3.141

Question 15

Explain the data type - TIME

Answer 15

Time is a data type that can store time values (hours, minutes & seconds). For
example, 03:15:00 (quarter past 3 am)

Question 16

Explain the data type - DATE

Answer 16

DATE is a data type that can store dates. The display format can be specified – e.g.
1/1/2017, 1 Jan 2017.

Question 17

Explain the data type - BOOLE

Answer 17

BOOLE is a data type that can store the values TRUE and FALSE

Question 18

What is data validation?

Answer 18

If incorrect data is entered into a database, the system will be less useful: in some instances it may even be dangerous.

For example, a well designed system ought to be able to prevent a user entering text data into a field that has been designed to store numeric data.

Validation is the automatic checking of data entered into a computer system.

Validation uses the properties of the data to identify any inputs that are obviously wrong.

Question 19

Explain the validation check- Presence Checks

Answer 19

It would be meaningless, for example, to attempt a bank withdrawal without specifying an account number. Consequently any form that enables the user to make such a withdrawal must ensure that the account number field is not left blank. This is an example of a presence check.

Question 20

Explain the validation check- Format Checks

Answer 20

Some data values are required to conform to given patterns. For example, UK post codes consist of two letters followed by three digits, followed by two letters. Consequently any relevant data entry form should check for this, and reject ill-formed postcodes. This is an example of a format check

Question 21

Explain the validation check- Length Checks

Answer 21

The number of characters in a name can vary, but it is difficult to imagine one that is less than three
characters long – or one that is more than twenty characters long. It would be reasonable to reject any
attempted data entry that contains a name that is outside these limits. This is an example of a length check.

Question 22

Explain the validation check- Type Checks

Answer 22

In a database that records the number of books in a bookstore, it would be strange to record a fractional number such as 36.4. Consequently any relevant data entry form should ensure that no fractional values are accepted. This is an example of a type check

Question 23

Explain the validation check- Range Checks

Answer 23

Human adults come in a range of heights, but it is difficult to imagine anyone shorter than (say) two feet or taller than (say) ten feet. It would be reasonable to reject any attempted data entry contains a height that falls outside of this range. This is an example of a range check

Question 23

What is a logical operator?

Answer 23

Comparing a value against other data is a typical operation when data is queried in a database.

Comparison operators allow this to be done. e.g. the comparison operator < indicates that the data entered must be less than a specified value for the result to be correct.

Also used to analyse to values and return a true or false result.

Question 24

What is a form?

Answer 24

Forms are a common way to collect data from people, they can be used to enter a new record, modify an existing record or view records already stored in the table.

When data is entered into a form, it is automatically added into the specified table and stored as part of the database.

Question 25

Advantages of forms

Answer 25

When there are a number of different tables in a database, forms make it easier to enter data as one form may include fields from different tables.

When the user enters data into the form the database software will ensure the data is stored in the correct table.

They can be used to control the type and format of the data ensuring that it is kept consistent and accurate.

Forms can also be customised to include a logo and colour.

Question 26

What is a Query?

Answer 26

A query is a way of searching and extracting data from a database to find the answer to a question.

The query/search checks each record and produces a list of data that satisfies the query criteria.

To create a query, criteria are added to one or more fields in the table.

Question 27

What is a Report?

Answer 27

A report allows tables and results from queries to be presented in user-friendly way.

The layout of the report can be customised, making it visually attractive and easy to read for the intended person or organisation.

The data can also be presented by grouping similar data or sorting it in ascending or descending order.

Question 28

What is a Macro?

Answer 28

A macro is a small program written to perform a repetitive database task automatically.

In a database, macros allow functionality to be added to both forms and reports such as adding a new record, deleting an old record or updating an existing record.

Instead of entering multiple instructions each time a task is performed, the user only needs to perform a single operation, such as clicking on a button, and the instruction stored within the macro are executed.

Question 29

What is big data?

Answer 29

The term Big Data has been used to refer to a range of problems and technologies that relate to the management of very large data sets.

The amount of data that we currently generate is enormous, and is increasing each year.

Question 30

State some sources of big data?

Answer 30

text, images and videos uploaded to social media sites

medical records,fitness monitors

financial markets – share price data, currencies, etc.;

Question 31

Explain volume in relation to Big Data?

Answer 31

Usually refer to the amount of data, it is difficult to put a size limit in what counts as big data; indeed what was considered big yesterday may not be considered big tomorrow.

It is clear, however, that big data problems involve data sets that are so large and complex that traditional tools, such as relational database management systems, are not able to deal with them effectively.

Question 32

Explain variety in relation to big data

Answer 32

Usually refers to the type of data or the way it is structured, much of the data being produced is unstructured – this is not data that can easily be put into relational database tables. It is video, audio, and image, as well as text and numeric data.

Question 33

Explain velocity in relation to big data?

Answer 33

Big data problems frequently have to deal with real time flows of data. Events happen in the real world and the data generated is real time, and is often time sensitive. For example:

CCTV Cameras or Stock exchange trades

Question 34

Who interprets big data and how?

Answer 34

Data analytics applies algorithms to raw data in order to spot patterns, relationships and trends. The algorithms may include statistical analysis as well as artificial intelligence techniques.

Question 35

What are some applications of analysing big data?

Answer 35

Healthcare, Crime prevention combat crime and energy management