Glossary
MySQL AUTO_INCREMENT
A column attribute that automatically assigns sequential integer IDs on INSERT — the standard primary key pattern in MySQL.
2mo ago
database beginner
MySQL charset=utf8mb4
PHP 5.1+
The correct MySQL character set for full Unicode support — including emoji and supplementary characters that the older utf8 charset cannot store.
2mo ago
php beginner
MySQL Connection Pooling
PHP 5.1+
Reusing database connections across requests instead of opening and closing a new connection on every request.
2mo ago
php intermediate
MySQL Date and Time Types
DATETIME, TIMESTAMP, DATE, TIME, and YEAR — each with different ranges, timezone handling, and storage sizes.
2mo ago
database beginner
MySQL DSN (Data Source Name)
PHP 5.1+
The connection string passed to PDO specifying the database driver, host, port, database name, and charset.
2mo ago
php beginner
MySQL ENUM Type
A column that accepts only predefined string values — stored efficiently as integers but with significant schema change pain.
2mo 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.
2mo 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.
2mo 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.
2mo ago
database intermediate
MySQL Index Types
B-tree, FULLTEXT, SPATIAL, and HASH indexes — each optimised for different query patterns.
2mo ago
database intermediate
MySQL JOIN Types
INNER JOIN, LEFT JOIN, RIGHT JOIN, and CROSS JOIN — controlling which rows are included when combining tables.
2mo 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.
2mo ago
database intermediate
MySQL LIMIT and OFFSET Pagination
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LIMIT restricts result row count; OFFSET skips rows for pagination — but OFFSET-based pagination degrades on large tables.
2mo 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.
2mo ago
database beginner
MySQL Numeric Types
INT, BIGINT, DECIMAL, FLOAT, DOUBLE — the right type prevents overflow, precision loss, and money calculation bugs.
2mo 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.
2mo 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.
2mo 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).
2mo 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.
2mo ago
database intermediate
Optimistic Locking
A concurrency pattern using a version column to detect conflicting concurrent writes — no row locks held between read and write.
2mo ago
database advanced