[DEE-5] Glossary
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Common terms used across DEE documents.
Database Fundamentals
| Term | Definition |
|---|---|
| ACID | Atomicity, Consistency, Isolation, Durability -- properties guaranteeing reliable transaction processing |
| BASE | Basically Available, Soft state, Eventually consistent -- alternative to ACID for distributed systems |
| CAP Theorem | A distributed system can guarantee at most two of: Consistency, Availability, Partition tolerance |
| DDL | Data Definition Language -- SQL statements that define schema (CREATE, ALTER, DROP) |
| DML | Data Manipulation Language -- SQL statements that manipulate data (SELECT, INSERT, UPDATE, DELETE) |
| Schema | The structure of a database: tables, columns, types, constraints, and their relationships |
| Transaction | A unit of work that is either fully completed or fully rolled back |
Relational Concepts
| Term | Definition |
|---|---|
| Normalization | Process of organizing data to reduce redundancy and improve integrity |
| Primary Key | A column (or set of columns) that uniquely identifies each row in a table |
| Foreign Key | A column that references the primary key of another table, enforcing referential integrity |
| Index | A data structure that improves query speed at the cost of additional storage and write overhead |
| Join | An operation combining rows from two or more tables based on a related column |
| Surrogate Key | An artificial key (e.g., auto-increment ID, UUID) with no business meaning |
| Natural Key | A key derived from real-world data (e.g., email, SSN) |
NoSQL Concepts
| Term | Definition |
|---|---|
| Document Store | Database storing data as semi-structured documents (e.g., MongoDB, CouchDB) |
| Key-Value Store | Database storing data as key-value pairs (e.g., Redis, DynamoDB) |
| Column-Family Store | Database organizing data into column families (e.g., Cassandra, HBase) |
| Graph Database | Database using graph structures with nodes, edges, and properties (e.g., Neo4j) |
| Eventual Consistency | A consistency model where replicas converge to the same state over time |
Operations
| Term | Definition |
|---|---|
| Replication | Copying data across multiple database instances for availability and read scaling |
| Sharding | Distributing data across multiple databases based on a partition key |
| Migration | A versioned change to the database schema |
| Connection Pool | A cache of database connections maintained for reuse |