Explain the purpose of Database System. Analyze One-to-One relationship and One-to-Many relationship in Database System with Example.

A database system (database + DBMS + users) stores large related data centrally with accuracy, security and quick retrieval — replacing scattered Excel files. Example: Nepal Police crime-record system instead of separate registers per station.

Purposes:

1. Removes duplication — Citizen name stored once, reused everywhere.
2. Ensures integrity — Validation + referential integrity block orphan/wrong entries.
3. Sharing and security — Many users with role-based access and logs.
4. Fast queries/reports — "List all cases in Surkhet in 2080" in seconds via SQL.
5. Recovery — Backup/restore after failure.

Relationships (terminology consistent across papers):

One-to-Many (1:M) — most common: One parent row links to many child rows. Example: One PoliceStation has many Officers.

• Implementation: PoliceStation.StationID (PK) → Officer.StationID (FK).
• In Access: Relationships window → drag StationID → Enforce Referential Integrity + Cascade Update. Deleting a station with officers is blocked, preventing orphans.

One-to-One (1:1): One row links to exactly one row. Example: Officer ↔ OfficerConfidential (medical/fingerprint kept in separate secure table).

• Implementation: link PK to PK/unique field. Used to split wide tables or isolate sensitive data with stricter permissions.

M:N (e.g. Officers ↔ Trainings) needs a junction table Assignment(OfficerID, TrainingID) — mention to show complete knowledge, but focus the answer on 1:1 vs 1:M as asked.