mysql-patterns

MySQL Patterns

Use this skill when working on MySQL or MariaDB schema design, migrations, slow-query investigation, queue-style transactions, connection pools, or production database configuration. Prefer exact version checks before applying a feature-specific pattern because MySQL and MariaDB have diverged in several SQL details.

Activation

• Designing MySQL or MariaDB tables, indexes, and constraints
• Reviewing migrations before they run on large production tables
• Debugging slow queries, lock waits, deadlocks, or connection exhaustion
• Adding keyset pagination, upserts, full-text search, JSON columns, or queues
• Configuring application connection pools, read replicas, TLS, or slow logs

Version Check

Start by identifying the engine and version:

SELECT VERSION();
SHOW VARIABLES LIKE 'version_comment';

Keep MySQL and MariaDB guidance separate when syntax differs:

• MySQL documents row aliases as the replacement for VALUES(col) in ON DUPLICATE KEY UPDATE; VALUES(col) is deprecated there.
• MariaDB documents VALUES(col) as the supported way to reference inserted values in ON DUPLICATE KEY UPDATE; use it for cross-engine compatibility.
• SKIP LOCKED is appropriate for queue-like work only. It skips locked rows and can return an inconsistent view, so do not use it for general accounting or integrity-sensitive reads.

Schema Defaults

CREATE TABLE orders (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    account_id BIGINT UNSIGNED NOT NULL,
    status VARCHAR(32) NOT NULL,
    total DECIMAL(15, 2) NOT NULL,
    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    deleted_at DATETIME NULL,
    PRIMARY KEY (id),
    KEY idx_orders_account_status_created (account_id, status, created_at),
    KEY idx_orders_active (account_id, deleted_at)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

Default choices: