Databases Glossary

Browse 73 databases terms defined in plain English, from the cultural dictionary of computing.

73 Databases Terms

ACID
An acronym for the four properties that guarantee reliable database transactions: Atomicity (all or nothing), Consistency (data stays valid), Isolation...
Automated Migration
A schema or data migration executed through versioned automation as part of an application's deployment or startup workflow instead of being applied manually....
Blob
Short for binary large object, a chunk of opaque data stored as a single value, often in databases, object storage, or browser APIs. Blobs are used for things...
B-tree
A self-balancing tree data structure that maintains sorted data and allows searches, insertions, and deletions in logarithmic time. B-trees and their variant...
Cascading Delete
A database behavior in which deleting a parent row automatically deletes related child rows according to foreign-key rules. Cascading deletes can simplify...
Cascading Update
A database behavior in which changes to a referenced parent key automatically propagate to related child records through foreign-key rules. Cascading updates...
CDC
Change Data Capture — a pattern for tracking and propagating changes made to a database by tailing its transaction log rather than polling for differences. CDC...
ClickHouse
A column-oriented database optimized for fast analytical queries over large datasets.
Cloud Database
A database service hosted and operated in the cloud, often provided as a managed offering with backups, replication, scaling, and maintenance handled by the...
CockroachDB
A distributed SQL database designed for resilience, horizontal scaling, and strong consistency across nodes.
Column Index
A database index built on one or more columns to speed lookups, filtering, joins, or sorting on those fields. Column indexes improve read performance...
column store
A database storage architecture that stores data by column rather than by row, enabling dramatic compression ratios and query performance for analytical...
Composite Index
A database index built on multiple columns in a defined order so queries filtering or sorting on those combined fields can be served efficiently. Composite...
connection pool
A cache of reusable database connections maintained by an application or middleware (like PgBouncer) to avoid the overhead of establishing a new connection for...
Cursor
A pointer or token representing a current position within a dataset, result set, or stream so processing can continue from that point. Cursors are common in...
CVE Database
A database or feed of Common Vulnerabilities and Exposures records used to track publicly identified software vulnerabilities. Teams use CVE databases for...
Database Activity Monitoring
The logging and analysis of database queries, sessions, privilege use, and anomalous behavior to detect misuse or support audits. Database activity monitoring...
Database Encryption
The use of encryption to protect database contents, whether at the file, disk, table, column, or field level. Its real strength depends on how keys are stored,...
Database Firewall
A security layer that inspects and controls database traffic or queries to block suspicious patterns, unauthorized statements, or policy violations. Database...
Database Security
The set of controls used to protect database systems and the data inside them, including authentication, authorization, encryption, patching, monitoring, and...
denormalization
The deliberate introduction of redundancy into a database schema to improve read performance, trading storage space and write complexity for faster queries....
DragonflyDB
An in-memory datastore positioned as a high-performance alternative for cache and key-value workloads.
Drop Table
A shorthand reference to deleting a database table, often invoked jokingly as the archetype of a dangerously powerful command. In engineering slang, 'drop...
foreign key
A column or set of columns in one table that references the primary key of another table, establishing a link between the two. Foreign keys enforce referential...
graph database
A database that uses graph structures — nodes, edges, and properties — to store and query highly connected data. Graph databases excel at relationship-heavy...
index
A data structure (typically a B-tree or hash table) that speeds up data retrieval operations on a database table at the cost of additional storage and slower...
Isolation Level
The transaction setting that defines how visible one transaction's intermediate or committed changes are to other concurrent transactions. Levels such as Read...
Join
A relational database operation that combines rows from two or more tables based on a related column or join condition. Different join types such as INNER,...
Join Table
An associative table used to represent a many-to-many relationship between two other tables, typically by storing one foreign key to each side. Join tables may...
Key-Value Store
A data store that associates each unique key with a value and retrieves data primarily by direct key lookup rather than relational joins or rich querying....
MariaDB
A community-developed relational database descended from MySQL and used in many web and application stacks.
Master-Slave
A replication or control architecture where one node (master/primary) accepts writes and propagates changes to one or more read-only nodes (slaves/replicas)....
materialized view
A database object that stores the precomputed results of a query physically on disk, unlike a regular view which re-executes the query each time. Materialized...
Metadata
Data that describes other data — such as a file's creation date, an image's resolution and EXIF tags, a database table's schema, or an API response's...
MVCC
Multi-Version Concurrency Control — a technique where the database maintains multiple versions of each row so that readers see a consistent snapshot without...
normalization
The process of organizing database tables to minimize redundancy and dependency, following a set of progressive rules called normal forms (1NF through 5NF)....
N Plus One Problem
A performance issue where one initial query triggers many additional dependent queries, often one per item, causing avoidable load and latency. In engineering...
Object-Relational Mapping
A technique (and family of libraries such as Hibernate, SQLAlchemy, and Prisma) that maps database tables to classes and rows to object instances, allowing...
Outer Join
A SQL join that returns all rows from one or both tables even when there is no matching row in the other table, filling in NULLs for the missing side. LEFT...
Partition
A division of a dataset, table, or topic into smaller, independent segments that can be stored, queried, or processed separately. In databases, partitions...
Partition Key
The column or attribute whose value determines which partition a given row or record is assigned to, via a hash or range function. Choosing a good partition...
Persistence
The characteristic of data that survives beyond the lifetime of the process that created it, typically by being written to durable storage such as a database,...
pgBouncer
A lightweight connection pooler for PostgreSQL that reduces database connection overhead and helps scale many clients.
query planner
The database component that analyzes a SQL query and determines the most efficient execution strategy — which indexes to use, what join order and algorithms to...
Redis Fork
A derivative project created from the Redis codebase, usually in response to governance, licensing, or strategic disagreement.
Replica
A copy of a database, service instance, or data partition that mirrors the primary's state, providing read scalability, fault tolerance, or geographic...
replication lag
The delay between when data is written to a primary database and when it appears on its read replicas. Replication lag causes the classic 'write then...
Right Join
A SQL join that returns all rows from the right (second) table and the matching rows from the left (first) table, filling in NULLs for left-table columns where...
RocksDB
A high-performance embedded key-value store developed by Facebook, built on a log-structured merge-tree (LSM-tree) architecture optimized for fast writes and...
Row-Level Security
A database feature (notably in PostgreSQL) that enforces access policies on individual rows within a table, so different users or roles only see and modify the...
Scalar
A single, indivisible value as opposed to a compound data structure like an array, object, or tuple. In databases, scalar types include integers, floats,...
Scan
An operation that reads through data sequentially. In databases, a full table scan examines every row (the fallback when no index applies); an index scan...
Search Index
A precomputed data structure — typically an inverted index mapping terms to the documents containing them — that enables fast full-text or structured queries...
Seed Data
An initial dataset loaded into a database to establish baseline records needed for the application to function — such as default roles, country codes, or test...
sharding key
The column or value used to determine which shard (partition) of a distributed database stores a given row. Choosing the right sharding key is one of the most...
Shared Nothing Architecture
A distributed system design in which each node has its own private CPU, memory, and storage with no shared resources between nodes, eliminating contention and...
Snapshot
A point-in-time capture of the complete state of a system — such as a filesystem, database, or virtual machine — that can be used for backup, recovery, or...
Snapshot Isolation
A database isolation model that gives each transaction a consistent snapshot while reducing read-write blocking. It shows up in application security, identity,...
SQL Injection Attack
An injection flaw where attacker-controlled input alters SQL queries to read, modify, or destroy database data. It shows up in application security, identity,...
stored procedure
A precompiled program stored in the database that encapsulates SQL statements and procedural logic, executed by calling its name rather than sending raw SQL....
Subquery
A SQL query nested inside another query, typically within a WHERE, FROM, or SELECT clause. The inner query executes first and its result is used by the outer...
TiDB
A distributed SQL database designed for horizontal scaling and MySQL-compatible usage patterns.
Time Series
A sequence of data points indexed by timestamp, typically collected at regular intervals — used for metrics, sensor readings, and financial data, and stored in...
time-series database
A database optimized for storing and querying data points indexed by time, such as metrics, sensor readings, and financial ticks. Time-series databases use...
Timestamp
A value representing a specific point in time, typically stored as seconds or milliseconds since the Unix epoch (January 1, 1970 UTC) or as an ISO 8601 string...
Transaction Log
An append-only, sequential record of every write operation performed on a database, written to disk before the actual data pages are modified (write-ahead...
trigger
A database object that automatically executes a specified function in response to certain events (INSERT, UPDATE, DELETE) on a table. Triggers enable automatic...
Update
The 'U' in CRUD — a write operation that modifies one or more fields of an existing record or resource in place, as opposed to creating a new record or...
UUID
Universally Unique Identifier — a 128-bit value formatted as five groups of hexadecimal digits (e.g., 550e8400-e29b-41d4-a716-446655440000) designed to be...
Valkey
An open-source in-memory data-store fork that emerged in response to licensing concerns around Redis.
WAL
Write-Ahead Log — a technique where all modifications are written to a sequential log file before being applied to the actual database pages. If the database...
Write Concern
A MongoDB setting that specifies the level of acknowledgment requested from the database for write operations — ranging from w:0 (fire and forget), w:1...
Write Lock
An exclusive lock acquired on a resource — such as a database row, file, or memory region — that prevents any other thread or process from reading or writing...

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