In database entity-relationship (ER) modeling, how many fundamental types of relationship cardinalities (mapping constraints) are categorized?
In database entity-relationship (ER) modeling, how many fundamental types of relationship cardinalities (mapping constraints) are categorized?
Multiple Choice Options
- A
1
- B
2
- C✓ Correct Option
3
- D
4
Detailed Technical Solution & Explanation
In relational database design and Entity-Relationship modeling, relationship cardinalities (mapping constraints between entities) are fundamentally grouped into 3 primary structural patterns based on relationship symmetry:
1. One-to-One (1:1)
2. One-to-Many / Many-to-One (1:N) (a single concept viewed from opposite perspective)
3. Many-to-Many (M:N)
*(Note: When Many-to-One is enumerated separately as an independent directional case, textbooks count 4 mapping constraints: 1:1, 1:N, N:1, and M:N).* In classical curriculum sets following Korth/Elmasri's core tripartite structural typology, the count is standardly answered as 3 (or 4 directional types).