What is the difference between SQL and NoSQL databases?

Question

Accepted Answer

**SQL** — relational, structured. **NoSQL** — non-relational, flexible.

**SQL (Relational):**
- Structured schema.
- ACID transactions.
- Complex queries (JOINs).
- Vertical scaling.

```
SQL:
  Tables with fixed schema
  SELECT * FROM users WHERE age > 25
  JOIN orders ON users.id = orders.user_id
  (Complex queries, ACID)
```

**NoSQL:**
- Flexible schema.
- BASE properties.
- Simple queries.
- Horizontal scaling.

```
NoSQL Types:
- Document: MongoDB
- Key-Value: Redis
- Column-Family: Cassandra
- Graph: Neo4j
(Flexible, scalable)
```

**Key differences:**
- **SQL** — structured, ACID.
- **NoSQL** — flexible, scalable.
- **SQL** — complex queries.
- **NoSQL** — simple queries.

Systems Analyst: What is the difference between SQL and NoSQL databases?