Databases

Question 1

What is an entity?

Answer 1

A table in a data base

Question 2

What is a field?

Answer 2

A column on a table

Question 3

What is a primary key?

Answer 3

The field which uniquely identifies every record in the entity

Question 4

What is a foreign key?

Answer 4

A primary key in a different entity

Question 5

What are the possible relationships between entities?

Answer 5

One-to-one, one-to-many and many-to-many

Question 6

What is data validation?

Answer 6

This is what makes sure data is sensible, reasonable, complete and within acceptable boundaries

Question 7

What is range check?

Answer 7

It is used for numbered data and it allows you to set suitable boundaries

Question 8

What is type check?

Answer 8

This is what makes sure the correct type of data has been entered into the field (e.g. String, Date, Integer etc.)

Question 9

What is “check digit”?

Answer 9

This checks a range of numbers to see if they have been entered correctly. This is usually for barcodes or ISBN numbers.

Question 10

What is length check?

Answer 10

This makes sure that the length of your data is correct. E.g. sometimes you need exactly 11 numbers (for phone numbers).

Question 11

What is “lookup”?

Answer 11

When you have a field which can only contain a limited list of items then a lookup is used to improve accuracy.

Question 12

What is picture/format check?

Answer 12

It is for when you have data which always consists of the same pattern. The format/picture check checks whether the data inputted fits the pattern.

Question 13

What is presence check?

Answer 13

It is when there is a field which cannot have any blank entries. The presence check checks whether something has been entered for each box.

Question 14

What is SQL?

Answer 14

It is the Standard Query Language used by database programs

Question 15

In SQL, what does SELECT do?

Answer 15

It extracts records from an entity without modifying them

Question 16

In SQL, what does the * mean?

Answer 16

It is the symbol for all records

Question 17

In SQL, what does FROM do?

Answer 17

It specifies which entity the data should be taken from

Question 18

In SQL, what is WHERE used to do?

Answer 18

It is used to make sure only data which fits a certain criteria is extracted

Question 19

In SQL, what is WHERE followed by?

Answer 19

A logical condition which must result in either true, false or null.

Question 20

In SQL, what are the main comparison conditions? (give symbols)

Answer 20

Equal to (=), not equal to (!=), greater than (>), less than (=) or less than or equal to (<=)

Question 21

In SQL, what are logic operations used for?

Answer 21

They allow more than one field at a time to be used to extract certain records

Question 22

What is an entity relationship diagram?

Answer 22

It is a diagram which describes the relationships between different entities

Question 23

In SQL, what are some examples of logic operations?

Answer 23

And, or, not

Question 24

Give the 6 main data types in a database and their properties.

Answer 24

1. Numeric (can only hold numbers (0-9))
2. Date/time (can only hold date (dd/mm/yyyy) or time (hh:mm:ss))
3. Boolean (can only hold true or false)
4. Binary (can only hold 1 or 0)
5. Varchar (variable data length, most commonly used with specific data sets like ASCII. This is defined during setup)
6. String

Question 25

What is DBMS? Give examples.

Answer 25

Database Management System; the software package that manages data. Examples include MS Access.