Following are the types of relationships used
in a database.
1. One-to-One Relationship
2. One-to-Many Relationship
3. Many-to-One Relationship
4. Many-to-Many Relationship
In One-to-One Relationship, one entity is
related with only one other entity. One row in a table is linked with only one
row in another table and vice versa.
For example: A student can have only one exam
In One-to-Many relationship, one entity is
related to many other entities.
One row in a table A is linked to many rows in
a table B, but one row in a table B is linked to only one row in table A. For
example: One Department has many staff members.
In Many-to-One Relationship, many entities can
be related with only one in the other entity.
For example: A number of staff members working
in one Department.
Multiple rows in staff members table is related
with only one row in Department table.
A many-to-many relationship occurs when
multiple records in a table are associated with multiple records in another
Example 1: Customers and Product
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