wp-database

# WordPress Custom Database Tables > **Model note:** `dbDelta` schema and CRUD patterns are mechanical (`haiku`). Query optimisation and multi-version data migrations require cross-file reasoning — use `sonnet` for those sub-tasks. Create and manage custom database tables in WordPress plugins: `dbDelta()` for schema definition, versioned upgrade routines, `$wpdb` CRUD with prepared statements, and data migration strategies. ## When to use - "Create a custom DB table for my plugin", "set up plugin schema with dbDelta". - "Write a migration for plugin upgrade", "run schema changes on update". - "Query a custom table", "insert/update/delete with $wpdb". - "Optimise a slow custom query", "add an index to a plugin table". - "Migrate data from post meta to a custom table". **Not for:** WooCommerce order table operations — use `wp-woocommerce`. General $wpdb query optimisation in core WP tables — use `wp-performance` (official skill). ## Method ### 1. Create table with dbDelta `dbDelta()` is the only WP-safe way to create and alter tables — it diffs the current schema against the SQL and applies only the necessary changes. ```php function my_plugin_create_tables() { global $wpdb; $charset_collate = $wpdb->get_charset_collate(); // e.g. DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci // $wpdb->prefix respects multisite site prefix automatically $table_log = $wpdb->prefix . 'my_plugin_log'; $table_meta = $wpdb->prefix . 'my_plugin_item_meta'...