Databases (CIE IGCSE Computer Science)

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Author

Amy Fellows

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Computer Science

Single Table Databases

A database is a structured collection of data so it can be searched, sorted, filtered and analysed quickly

Data in a database can be any type of data including text, images, videos, sound

Databases use tables to store data
Tables have records of data represented by one row

In the example below, each row represents the data stored about a single customer (the customer’s record)
In the customer table there are 3 records
Each record is divided into fields (CustomerID, FirstName, LastName, DOB and Phone Number)

A Database Table Containing Customer Details

CustomerID	FirstName	LastName	DOB	PhoneNumber
1	Andrea	Bycroft	05031976	0746762883
2	Melissa	Langler	22012001	0756372892
3	Amy	George	22111988	0746372821

Fields are represented by the columns in a table

There are 5 fields in the customer table
The first row in a table contains the field names which is the heading for the data stored in that field
Each field in a table has a data type which defines what data can be entered into that field

Worked example

A Database Table Containing Pet Details

DogID	Name	Breed	Age	Gender
DG12	Smokey	Poodle	12	M
DG34	Harvey	Springer Spaniel	10	M
DG48	Maisie	Labradoodle	3	F
DG49	Maggie	Labradoodle	3	F
DG88	Winston	Bulldog	7	M
DG95	Shona	Golden Retriever	6	F

How many fields are there in the Dogs table shown above?

[1]

5 [1]

How many records are there in the Dogs table?

[1]

6 [1]

Exam Tip

It is very likely you will be presented with an example database table and identify either how many fields there are or how many records there are so make sure you remember a record is row and a field is a column

Validation and Verification

Verification checks check whether the data that has been entered is the correct data and is accurate

This is often completed by getting data entered by one person is then checked by another person

When a table is created, validation rules can be assigned to the different fields

A validation rule controls what data can be entered into that field
There are different types of validation checks used to limit what data can be entered into each field

The different types of validation check

Type	Description
Length Check	This type of validation checks the number of characters that have been entered into a field. For example, you might make phone numbers entered have to be eleven characters long
Format Check	This type of validation checks data entered meets an exact format. For example, a product code might have to be two letters followed by five numbers
Range Check	A range check will check the number entered is within a specific range. For example, the age of a dog would be between 0 - 40. Any other number would be disallowed
Presence Check	A presence check can be added to fields which cannot be left blank
Type Check	A type check will allow data with a specific data type to be entered into a field. For example, if text was entered into a field which is supposed to contain the date of birth of a person it would not be allowed
Check Digits	Check digit validation is a process used to verify the accuracy of numbers such as credit card numbers. A check digit is a single digit added to the end of the number, which is calculated based on a specific algorithm applied to the other digits in the number. When the data is re-entered the same algorithm can be applied and if it produces a different result the code is incorrect

Worked example

A Database Table Containing Student Grades

StudentID	FirstName	LastName	MarkSubmitted	Percentage
1483792	Shanay	Giles	Y	55
1498378	Poppy	Petit	N	20
1500121	Diya	Dinesh	Y	74
1382972	Joe	Swaile	Y	68
1598264	Anton	Smith	Y	34
1548282	Felicity	Hall	N	47

Describe two validation checks that could be used to check data being inputted into the table above

[4]

StudentID could have a length check to ensure 7 characters are entered [2]

FirstName and LastName could have a presence check to make a record cannot be entered without entering the name of the student [2]

A type check of boolean could be applied to the Mark Submitted field so that only Y or N are entered [2]

A range check could be assigned to the Mark column to ensure only numbers between 0 and 100 are entered [2]

Data Types

Table fields are represented by columns in a table
There are 5 fields in the customer table below

These include CustomerID, FirstName, LastName, DOB and PhoneNumber

A Database Table Containing Customer Details

CustomerID	FirstName	LastName	DOB	PhoneNumber
1	Andrea	Bycroft	05031976	0746762883
2	Melissa	Langler	22012001	0756372892
3	Amy	George	22111988	0746372821

Each field in a table, has a data type

Common data types include text/alphanumeric, character, boolean, integer, real and date/time
Phone numbers have to be assigned the text/alphanumeric data type because they begin with a 0

If you assigned the data type Integer to a phone number it would remove the initial 0

Database Data Types

Data Type	Explanation	Example
Text/Alphanumeric	This data type allows letters, special characters like spaces and punctuation and numbers to be entered into a field	NG321AE
Character	This allows single characters to be entered into a field. Characters can be any alphanumeric value and can be lowercase or uppercase	A
Boolean	This data type can be used in fields where there are only two possible options. Data is stored as a 1 or 0 in the database but can be used to represent True/False or Yes/No	True/False
Integer	Only whole numbers can be entered	15
Real	Numbers including decimal numbers can be stored	30.99
Date/Time	Only dates or times can be entered into a field with this type. A format for the date/time can also be assigned to the field	180855

Worked example

A Database Table Containing Dog Details

DogID	Name	Breed	Age	Gender
DG12	Smokey	Poodle	12	M
DG34	Harvey	Springer Spaniel	10	M
DG48	Maisie	Labradoodle	3	F
DG49	Maggie	Labradoodle	3	F
DG88	Winston	Bulldog	7	M
DG95	Shona	Golden Retriever	6	F

What data type should Age be?

[1]

Integer [1]

What data type should DogID be?

[1]

Text/Alphanumeric [1]

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Databases (CIE IGCSE Computer Science)

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Author: Amy Fellows