Relationships (One-to-One, One-to-Many, Many-to-Many)

Relationships in data describe how entities connect. In a **one-to-one** relationship, each item in one group relates to exactly one in another (e.g., a person and their passport). In a **one-to-many** relationship, one entity links to multiple entities in another group (e.g., a doctor and their patients). A **many-to-many** relationship involves multiple items on both sides (e.g., students and courses). These relationships help organize data efficiently and clarify how different pieces of information are associated within a system.