Question

Explain the different types of relationship mapping.

Answer 1

The types of relationships used in a database are

• One-to-One Relationship
• One-to-Many Relationship
• Many-to-One Relationship
• Many-to-Many Relationship

One-to-One Relationship:

• In One-to-One Relationship, one entity is related to only one other entity.
• One row in a table is linked with only one row in another table and vice versa. Example: A student can have only one exam number.

One to one Relationships

One-to-Many Relationship:

• In a One-to-Many relationship, one entity is related to many other entities.
• One row in table A is linked to many rows in table B, but one row in table B is linked to only one row in table A. Example: One Department has many staff members.

One to Many Mapping

Many to-one Relationship:

• In Many-to-One Relationship, many entities can be related with only one in the other entity.
• Example: A number of staff members working in one Department. Multiple rows in staff members table are related with only one row in Department table.

Many to one Relationship

Many-to-Many Relationship:

• A many-to-many relationship occurs when multiple records in a table are associated with multiple records in another table.
• Example 1: Customers and Product

Many to Many Relationship

Customers can purchase various products and Products can be purchased by many customers.

Example 2: Students and Courses
A student can register for many Courses and a Course may include many students.

Example 3: Books and Student.
Many Books in a Library are issued to many students.