Cardinality question: a single entity instance of one type is related to many entity instances of another type. What cardinality is this?

Introduction / Context:
Understanding relationship cardinalities is essential for correct schema design, foreign key placement, and query formulation.

Given Data / Assumptions:

• Exactly one instance on the first side relates to several instances on the second side.
• There is no implication of multiple instances back to the first side.

Concept / Approach:
A “one-to-many” relationship connects one parent to many children. Typical mappings place the foreign key on the many side (child table) pointing to the one side (parent table).

Step-by-Step Solution:

Verification / Alternative check:
Common examples: one Customer has many Orders; one Department has many Employees.

Why Other Options Are Wrong:

• One-to-one: at most one on each side.
• Many-to-many: many on both sides.
• Composite relationship: not a standard cardinality term here.

Common Pitfalls:
Misplacing foreign keys by putting them on the one side. In relational design, the many side holds the foreign key to the one side.

Final Answer:
One-to-Many Relationship