Fundamental Database Concepts & Conceptual Modeling

Without a database, data is hard-coded in applications or kept in flat files — every application manages its own data, code and data are entangled.

The 4 problems a DBMS solves:

1. Application programs ↔ data separation: Data is stored independently from the code that uses it — schema changes don't require rewriting all applications.

2. Data usage ↔ data management separation: Who uses the data and how it is stored are decoupled.

3. Declarative data access: User says what they want, not how to retrieve it. Example: SELECT name FROM students WHERE age > 20 — the DBMS figures out index traversal.

4. Multiple user views: Different users see different views of the same data with controlled access rights (e.g. doctor sees full patient record; receptionist sees only appointment info).

DBMS: The software system providing all these functions. Examples: PostgreSQL, MySQL, Oracle, MongoDB.