What is the difference between conceptual, logical, and physical data models?

Question

Accepted Answer

**Conceptual** — high-level entities. **Logical** — detailed attributes. **Physical** — actual implementation.

**Conceptual Model:**
- High-level entities.
- Business relationships.
- No attributes.
- Stakeholder communication.

```
Conceptual: Customer → places → Order → contains → Product
```

**Logical Model:**
- Entities with attributes.
- Data types.
- Relationships with cardinality.
- Platform independent.

```
Logical: Customer(id, name, email) 1:M Order(order_id, date, total)
```

**Physical Model:**
- Actual tables and columns.
- Indexes, constraints.
- Platform specific.
- SQL DDL.

```
Physical: CREATE TABLE customers (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100) NOT NULL
);
```

**Progression:** Conceptual → Logical → Physical.

Systems Analyst: What is the difference between conceptual, logical, and physical data models?