What is a primary key?

a field that uniquely identifies each record. No two records can share its value.

Which data type suits a field recording whether a fee has been paid?

Boolean. It has two values: yes or no.

Which data type should be used for a telephone number?

text. Leading zeros would be lost in a numeric field.

What is a flat file database?

a database with a single table. Data is often repeated in it.

What does a foreign key do?

links a table to another table. It holds the primary key of the other table.

Which is a feature of a good data entry form?

drop-down lists to reduce typing. Choosing from a list prevents spelling errors.

Databases: structure, keys and forms · Cambridge IGCSE Information & Communication Technology

In plain words

A database is an organised collection of data. Before any data goes in, its structure has to be designed: what tables there are, what fields each has, what type of data each field holds, and how the tables are linked.

7 things to know

A table holds data in records (rows) and fields (columns).
Data types: text (also called alphanumeric), numeric (integer, decimal or currency), date/time, and Boolean (also called logical), which has two values, such as yes and no. A Boolean field can be shown as yes/no, true/false or a checkbox.
A flat file database is a single table. It is simple to set up, but the same data is often repeated in many records, which wastes storage and leads to mistakes when it is changed.
A relational database has two or more tables that are linked. Each item of data is stored once, so there is less duplication, and a change made in one place applies everywhere. It is more complex to design.
A primary key is a field that uniquely identifies each record in a table.
A foreign key is a field in one table that is the primary key of another table. It is what links the two tables.
A good data entry form has a clear title and labels, fields in a logical order, boxes of a suitable size, drop-down lists and tick boxes to reduce typing, clear navigation buttons and enough white space.

Worked example

A library has a Books table (with BookID) and a Loans table that records which book was lent to which member. How are the tables linked?

BookID is the primary key of the Books table: it identifies each book.
The Loans table has a BookID field too. There it is a foreign key.
The foreign key links each loan to one record in the Books table, so the book's details are not repeated in every loan.

Tips and tricks

A telephone number is text, not numeric: no arithmetic is done with it, and a leading zero must be kept.
Primary key: unique in its own table. Foreign key: a primary key from another table, used as the link.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Databases: structure, keys and forms: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What is a primary key?
- the first record in a table
- a field that uniquely identifies each record (the answer)
- a password for the database
- a field that can be left empty
No two records can share its value.
Which data type suits a field recording whether a fee has been paid?
- text
- numeric
- date/time
- Boolean (the answer)
It has two values: yes or no.
Which data type should be used for a telephone number?
- text (the answer)
- integer
- currency
- Boolean
Leading zeros would be lost in a numeric field.
What is a flat file database?
- a database with linked tables
- a database with a single table (the answer)
- a database with no fields
- a database stored on paper
Data is often repeated in it.
What does a foreign key do?
- encrypts a table
- links a table to another table (the answer)
- sorts the records
- deletes duplicates
It holds the primary key of the other table.
Which is a feature of a good data entry form?
- no labels
- very small boxes
- drop-down lists to reduce typing (the answer)
- fields in a random order
Choosing from a list prevents spelling errors.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 6 marks. Write your answers on paper, then check them.

Databases: structure, keys and forms

Cambridge IGCSE Information & Communication Technology 0417 · 6 marks · papermunch.org

Name ______________________________ Date ______________

Give two advantages of a relational database compared with a flat file database.[2]
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Data is not duplicated, so less storage is used. Data only has to be changed in one place, so it stays consistent.
I got this one
Describe the difference between a primary key and a foreign key.[2]
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A primary key is a field that uniquely identifies each record in its table. A foreign key is a field that is the primary key of another table, and links the two tables.
I got this one
State two features of a well-designed data entry form.[2]
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Clear labels for each field. Drop-down lists or tick boxes to reduce typing errors. (Also: a logical order of fields, navigation buttons.)
I got this one

Answers: Databases: structure, keys and forms

1. Data is not duplicated, so less storage is used. Data only has to be changed in one place, so it stays consistent.
2. A primary key is a field that uniquely identifies each record in its table. A foreign key is a field that is the primary key of another table, and links the two tables.
3. Clear labels for each field. Drop-down lists or tick boxes to reduce typing errors. (Also: a logical order of fields, navigation buttons.)