Database terms
Where your data lives, breathes, and occasionally panics
Almost every application is, at its core, a system for reading and writing data. This category covers relational and non-relational databases, query optimisation, indexing strategies, transactions, normalisation, replication, and the CAP theorem trade-offs that dictate how distributed data behaves. Choosing and using the right database correctly is one of the highest-leverage skills in backend development.
More on Database
History
Databases emerged in the 1960s as a solution to manage large volumes of structured data, with hierarchical and network models preceding the relational model proposed by Edgar F. Codd in 1970. The relational paradigm dominated enterprise computing through systems like Oracle, IBM DB2, and MySQL, standardizing SQL as the universal query language by the 1980s–90s. The 2000s saw the rise of NoSQL databases in response to web-scale demands for unstructured data and horizontal scalability, while distributed systems and cloud infrastructure reshaped deployment patterns. Modern practice now spans a spectrum: traditional ACID-compliant relational databases, document stores, time-series systems, and graph databases coexist, with teams selecting tools based on consistency guarantees, query patterns, and operational complexity. Today's database engineering emphasizes replication, sharding, monitoring, and migration safety as foundational practices rather than afterthoughts.
Key concepts
- Database Schema Design
- Database Indexes
- Database Transactions
- Database Normalisation
- Foreign Keys & Referential Integrity
- Query Optimisation
- Transaction Isolation Levels
- Database Views & Materialised Views
Best references
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PostgreSQL Official Documentation Comprehensive, authoritative reference covering transactions, indexes, query planning, replication, and advanced features like window functions and CTEs. Gold standard for PostgreSQL-specific topics.
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MySQL 8.0 Reference Manual Official MySQL documentation detailing storage engines (InnoDB vs MyISAM), index types, JSON support, AUTO_INCREMENT, and query optimization. Essential for MySQL-specific implementation details.
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Database Internals by Alex Petrov Modern reference covering storage engines, indexing strategies, write-ahead logs, transactions, and replication fundamentals. Bridges theory and practical implementation across database systems.
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SQL Performance Explained by Markus Winand Focused resource on query optimization, index design, execution plans, and performance anti-patterns like N+1 queries. Vendor-agnostic but deeply technical.
✦ Latest in Database
Typed relationships here
Edges touching a Database term.
- Column-Level Encryption Often seen in Database Schema Design 5d
- Query Optimisation Leverages Database Indexes Jun 13
- SQLite in Production Leverages Write-Ahead Log (WAL) Jun 10
- Write-Ahead Log (WAL) Enables ACID Properties Jun 10
- Write-Ahead Log (WAL) Often seen in SQLite in Production Jun 9
Document stores like MongoDB and CouchDB expose query languages that accept rich operator objects ($ne, $gt, $where), so unsanitized attacker input becomes NoSQL injection — the carrier that turns a query into a weapon. That injection smuggles a subverted query into the authentication layer, bypassing password checks or dumping credentials, which is exactly the foothold that leads to full account takeover. Remove NoSQL injection and the document store has no path to account takeover at all — the mediator is the entire mechanism.
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Database Bulk Operations
PHP 7.0+
Process many rows in a single SQL statement or batched transaction instead of one round-trip per row, for far higher throughput.
6d ago
Database intermediate
Database Query Result Streaming
PHP 8.0+
2
Processing large result sets row-by-row without loading the entire dataset into memory - essential for PHP CLI scripts handling millions of rows.
2mo ago
Database intermediate
InnoDB vs MyISAM
InnoDB is the default MySQL storage engine supporting transactions, foreign keys, and row-level locking — MyISAM is legacy with table-level locking and no transaction support.
3mo ago
Database beginner
INSERT ... ON DUPLICATE KEY UPDATE
PHP 5.1+
An atomic MySQL upsert — inserts a new row or updates the existing one if a unique key constraint would be violated.
3mo ago
Database intermediate
MySQL AUTO_INCREMENT
A column attribute that automatically assigns sequential integer IDs on INSERT — the standard primary key pattern in MySQL.
3mo ago
Database beginner
MySQL Date and Time Types
DATETIME, TIMESTAMP, DATE, TIME, and YEAR — each with different ranges, timezone handling, and storage sizes.
3mo ago
Database beginner
MySQL ENUM Type
A column that accepts only predefined string values — stored efficiently as integers but with significant schema change pain.
3mo ago
Database beginner
MySQL EXPLAIN
A MySQL query analysis command showing the execution plan — which indexes are used, how many rows are scanned, and where bottlenecks are.
3mo ago
Database intermediate
MySQL FULLTEXT Search
A built-in MySQL search engine supporting natural language and boolean full-text queries on TEXT and VARCHAR columns.
3mo ago
Database intermediate
MySQL GROUP BY and Aggregates
GROUP BY collapses rows with matching column values into one — aggregate functions (COUNT, SUM, AVG, MAX, MIN) compute values per group.
3mo ago
Database intermediate
MySQL Index Types
B-tree, FULLTEXT, SPATIAL, and HASH indexes — each optimised for different query patterns.
3mo ago
Database intermediate
MySQL JOIN Types
INNER JOIN, LEFT JOIN, RIGHT JOIN, and CROSS JOIN — controlling which rows are included when combining tables.
3mo ago
Database beginner
MySQL JSON Column Type
A native JSON storage type introduced in MySQL 5.7 that validates, indexes, and queries JSON documents with dedicated functions.
3mo ago
Database intermediate
MySQL LIMIT and OFFSET Pagination
1
LIMIT restricts result row count; OFFSET skips rows for pagination — but OFFSET-based pagination degrades on large tables.
3mo ago
Database intermediate
MySQL NULL Handling
NULL in SQL represents an unknown value — it is not zero, not empty string, and comparisons with = NULL are always false.
3mo ago
Database beginner
MySQL Numeric Types
INT, BIGINT, DECIMAL, FLOAT, DOUBLE — the right type prevents overflow, precision loss, and money calculation bugs.
3mo ago
Database beginner
MySQL Query Cache (Deprecated)
A server-side cache for SELECT results removed in MySQL 8.0 — it caused severe scalability issues under concurrent writes.
3mo ago
Database intermediate
MySQL String Types: VARCHAR vs TEXT vs CHAR
CHAR is fixed-length, VARCHAR is variable-length up to 65,535 bytes, TEXT variants store large content — each with different indexing and storage behaviour.
3mo ago
Database beginner
MySQL Subqueries
A query nested inside another — useful for filtering and deriving values, but correlated subqueries re-execute per outer row and can be O(n²).
3mo ago
Database intermediate
N+1 Query Problem
PHP 5.1+ A performance anti-pattern where fetching N records triggers N additional queries — one per record — instead of a single JOIN.
3mo ago
Database intermediate