WordPressプラグイン作成 - データベース テーブル作成

createDatabaseTable.php

<?php
public function createDatabaseTable()
{
    global $wpdb;

    $charsetCollate = $wpdb->get_charset_collate();

    $sql = "CREATE TABLE {$this->tableName} (
        id VARCHAR(8) NOT NULL,
        datetime_register DATETIME DEFAULT CURRENT_TIMESTAMP NOT NULL,
        datetime_renewal DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL,
        name VARCHAR(20) NOT NULL,
        data TEXT NOT NULL,
        PRIMARY KEY (id)
    ) {$charsetCollate};";

    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );
}
?>