Quick Summary
Databases store and organize data for easy access, management, and updating. They use DBMS software to manage operations.
A database is an organized collection of structured information or data stored electronically in a computer system. Databases are controlled by Database Management Systems (DBMS) that handle data storage, retrieval, and manipulation.
Types of Databases
| Type | Description | Examples |
|---|---|---|
| Relational (SQL) | Table-based with relationships | MySQL, PostgreSQL, Oracle |
| NoSQL | Non-relational, flexible schema | MongoDB, Cassandra, Redis |
| Document | Stores JSON-like documents | MongoDB, Couchbase |
| Key-Value | Simple key-value pairs | Redis, DynamoDB |
| Graph | Node and relationship focused | Neo4j, Amazon Neptune |
Database Operations (CRUD)
- Create: Insert new data
- Read: Retrieve data (query)
- Update: Modify existing data
- Delete: Remove data
SQL vs NoSQL
| Feature | SQL | NoSQL |
|---|---|---|
| Schema | Fixed, predefined | Flexible, dynamic |
| Scalability | Vertical | Horizontal |
| Best For | Complex queries, ACID | Big data, rapid scaling |
Popular Database Systems
- MySQL: Popular open-source relational DB
- PostgreSQL: Advanced open-source relational DB
- MongoDB: Leading NoSQL document DB
- Redis: In-memory key-value store
- SQLite: Lightweight, serverless database
Key Points
- Organized data collection
- SQL and NoSQL types
- CRUD operations
- Relational uses tables
- NoSQL is schema-flexible
- MySQL and PostgreSQL popular