One-to-One Relationship

• In a one-to-one relationship, a record in one table is associated with at most one record in another table.
• Example: A person can have only one passport, and a passport can belong to only one person.

One-to-Many Relationship

• In a one-to-many relationship, a record in one table can be associated with multiple records in another table.
• Example: A customer can place multiple orders, but each order is associated with only one customer.

Many-to-One Relationship

• This is the inverse of a one-to-many relationship.
• Example: Multiple students can enroll in the same course, but each student enrollment is associated with only one course.

Many-to-Many Relationship

• In a many-to-many relationship, multiple records in one table can be associated with multiple records in another table.
• Example: A student can enroll in multiple courses, and a course can have multiple students enrolled.

2 marks for identifying any two different types of relationships within databases.

Definition

A database transaction is 1 mark:

• a unit of work/logical action
• performed on a database
• independent of other transactions
• changes state of the database

Example Answers

Example answer 1 A database transaction is a logical unit that is independently executed for data retrieval or updates. 2 marks

Example answer 2 A database transaction is a unit of work that is either executed in full or not executed at all. 2 marks

Example answer 3 A database transaction is a way of representing a state change and has four properties, known as ACID. 2 marks

Example answer 4 A database transaction is usually means a sequence of steps, treated as a unit for the purposes of satisfying a client's request. 2 marks

Example answer 5 A database transaction is a process carried out on a database which may change its state, for example: moving money between bank accounts. 2 marks

Award 10 marks maximum

Part 1

Identify two different types of relationships within databases.

2 max

• One to one
• One to many
• Many to one
• Many to many

Part 2

Define the term database transaction.

2 max

Award 1 for:

• a unit of work/logical action;
• performed on a database;
• independent of other transactions;
• changes state of the database;

Example answer 1 A database transaction is a logical unit that is independently executed; For data retrieval or updates;

Example answer 2 A database transaction is a unit of work; That is either executed in full or not executed at all;

Example answer 3 A database transaction is a way of representing a state change; And has four properties, known as ACID;

Example answer 4 A database transaction usually means a sequence of steps, treated as a unit; For the purposes of satisfying a client's request;

Example answer 5 A database transaction is a process carried out on a database; Which may change its state, for example: moving money between bank accounts;

Part 3

Explain the importance of durability in a database transaction.

2 max

Example answer 1 Durability is important because transaction data changes must be available; Even in the event of database failure;

Example answer 2 Durability means that if the system says the transaction has been committed; The client does not need to worry about it because transactions that have been committed will survive permanently;

Example answer 3 Durability in databases is an important property because it ensures transactions are saved permanently; And do not accidentally disappear or get erased;