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A database is an organized collection of data stored electronically. Think of it like a digital filing cabinet that's incredibly fast at finding, organizing, and managing information.
Why We Need Databases:
- Persistence: Data survives after your program closes
- Organization: Structured storage with relationships
- Efficiency: Fast queries and updates
- Concurrency: Multiple users can access data safely
- Integrity: Rules ensure data stays consistent
Types of Databases:
- Relational (SQL): Data in tables with relationships (MySQL, PostgreSQL)
- NoSQL: Flexible schemas (MongoDB, Redis)
- Graph: For connected data (Neo4j)
- Time-series: For metrics and logs (InfluxDB)
Key Concepts:
- Tables/Collections: Where data is stored
- Queries: How you ask for data
- Transactions: Groups of operations that succeed or fail together
- Indexes: Structures that speed up lookups
FAQ
What's the difference between SQL and NoSQL?
SQL databases use structured tables and relationships. NoSQL databases are more flexible, using documents, key-value pairs, or graphs.
Do I need a database for my app?
If you need to store data that persists between sessions, yes. Simple apps might use files, but databases are better for complex data.
What's a database transaction?
A group of operations that either all succeed or all fail. Like transferring money: both accounts must update, or neither does.