MySQL / MariaDB Skill

Query Standards

• Use ANSI SQL join syntax (JOIN ... ON ...) — never comma-separated joins in FROM.
• Always alias tables: SELECT u.name FROM users AS u.
• Use UPPER_CASE for SQL keywords; snake_case for identifiers.
• Use prepared statements / parameterized queries for all user-supplied values — never concatenate strings into SQL.
• Format complex queries with consistent indentation; each clause on its own line.

Schema Design

• Use INT UNSIGNED for auto-increment primary keys; prefer BIGINT UNSIGNED for large tables.
• Use AUTO_INCREMENT for surrogate primary keys.
• Always define NOT NULL with a DEFAULT for mandatory columns.
• Use soft delete: add a deleted_at DATETIME NULL DEFAULT NULL column — never DELETE user-facing records.
• Use DATETIME for timestamps (timezone-aware at the application layer); use TIMESTAMP only for auto-managed created_at/updated_at.
• Use utf8mb4 charset and utf8mb4_unicode_ci collation for full Unicode support (including emoji).
• Schema changes require team lead approval.