1. Data Storage
- Data Organization: Data is stored in tables, which consist of rows and columns. Each table represents a different entity (like a customer, product, or transaction).
- Data Types: Each column in a table is assigned a specific data type (e.g., integer, string, date) to ensure data integrity.
- Files and Pages: At the lowest level, data is stored on the disk in files. These files are divided into pages, which are the basic unit of data storage in a database.
2. Database Management System (DBMS)
- DBMS: This is the software layer that interacts with the user or application to manage the database. Popular DBMSs include MySQL, PostgreSQL, Oracle, and Microsoft SQL Server.
- Query Processing: Users interact with the database using SQL (Structured Query Language). The DBMS parses, optimizes, and executes these queries to retrieve or manipulate data.
- Transaction Management: Databases support transactions, which are sequences of operations that are treated as a single unit. The DBMS ensures that transactions are executed completely (commit) or not at all (rollback), ensuring data consistency.
3. Indexing
- Indexes: To speed up data retrieval, databases use indexes. An index is a data structure that allows the DBMS to locate data quickly without scanning the entire table.
- Types of Indexes: Common types include B-tree indexes, hash indexes, and full-text indexes, each optimized for different types of queries.
4. Concurrency Control
- Locking Mechanisms: When multiple users or applications access the database simultaneously, the DBMS uses locks to prevent conflicts and ensure data integrity.
- Isolation Levels: The DBMS provides different isolation levels to control how transactions interact with each other, balancing between data consistency and performance.
5. Backup and Recovery
- Data Backup: Databases periodically back up data to prevent loss due to hardware failure, corruption, or other issues.
- Recovery Mechanisms: If a system failure occurs, the DBMS uses recovery techniques to restore the database to a consistent state using logs and backups.
6. Security
- Authentication and Authorization: The DBMS controls who can access the database and what operations they can perform.
- Encryption: Data can be encrypted to protect it from unauthorized access, both at rest and in transit.
7. Performance Optimization
- Query Optimization: The DBMS uses algorithms to determine the most efficient way to execute a query.
- Caching: Frequently accessed data may be stored in memory (cache) to speed up retrieval.
- Partitioning: Large tables can be divided into smaller, more manageable pieces (partitions) to improve performance.
8. Replication and Sharding
- Replication: Data can be copied across multiple servers to increase availability and reliability.
- Sharding: In distributed systems, a large database can be split into smaller, more manageable pieces (shards), each hosted on different servers.
