Relational Databases
Overview
Write a customer's address on every order they place and you have created a problem you will not notice for months. Then they move. Now some orders carry the old address and some carry the new one, both are in the same file, and nothing in the data says which is correct. The information has not been lost. It has been duplicated, and duplication is how data becomes untrustworthy.
This lesson explains what a database is, what makes one relational, and the five terms the specification examines: table, record, field, primary key and foreign key. Then it explains the reason the whole design exists. Splitting data across linked tables so that each fact is stored exactly once is what makes redundancy and inconsistency avoidable, and being able to say precisely how it does that is worth more marks than being able to name the parts.
Objectives
- Explain the concept of a database. Explain the concept of a relational database. Understand the following important database concepts.
- table
- record
- field
- primary key
- foreign key.
- Understand that the use of a relational database facilitates the elimination of data inconsistency and data redundancy.
Mind map
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Relational Databases. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- What is a record in a relational database? A. One column of a table B. All the data about one individual item, held as one row C. The name of a table D. A link between two tables Answer: B
- What is a primary key? A. A field whose value uniquely identifies each record in a table B. The first field listed in a table C. A field that holds a value from another table D. The password used to open the database Answer: A
- A Booking table contains a field MemberID which holds values from the Member table's primary key. What is MemberID in the Booking table? A. A primary key B. A record C. A foreign key D. A table Answer: C
- What is data redundancy? A. Data that is no longer needed and can be deleted B. Storing the same piece of data more than once C. Data that has been encrypted D. A field with no value in it Answer: B
- Why can data inconsistency not occur if a fact is stored exactly once? A. Because a single copy cannot disagree with anything B. Because single copies are always encrypted C. Because a single copy takes up less space D. Because tables cannot be linked Answer: A
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