AccentureDatabaseMedium
What is the difference between SQL and NoSQL databases?
SQLNoSQLDatabaseMongoDBMySQL
Question
Explain the differences between SQL and NoSQL databases. When would you choose one over the other?
Answer
SQL Databases (Relational):
- Structured data with predefined schema
- ACID properties (Atomicity, Consistency, Isolation, Durability)
- Vertical scaling (scale up)
- Complex queries with JOINs
- Examples: MySQL, PostgreSQL, Oracle
NoSQL Databases (Non-relational):
- Unstructured or semi-structured data
- Flexible schema
- Horizontal scaling (scale out)
- Simple queries, no JOINs
- Examples: MongoDB, Cassandra, Redis
Key Differences:
| SQL |
| NoSQL |
| ----- |
| ------- |
| Table-based |
| Document, Key-Value, Graph, Column |
| Fixed schema |
| Dynamic schema |
| ACID compliant |
| BASE (Basically Available, Soft state, Eventual consistency) |
| Vertical scaling |
| Horizontal scaling |
| Complex queries |
| Simple queries |
When to Use SQL:
- Structured data with relationships
- Need ACID compliance
- Complex queries and transactions
- Data integrity is critical
When to Use NoSQL:
- Unstructured or semi-structured data
- Need horizontal scaling
- Rapid development
- Big data and real-time applications
Explanation
The choice between SQL and NoSQL depends on your specific requirements. Many modern applications use both - SQL for transactional data and NoSQL for analytics, caching, or document storage.