Test dbDelta

my-plugin.php

<?php
/*
Plugin Name: My Plugin
Description: Test dbDelta
Version: 0.1
*/

// Upgrade when the admin loads
add_action( 'admin_init', 'myplugin_upgrade' );

// Activation & Deactivation hooks
register_activation_hook( __FILE__, 'myplugin_activate' );
register_deactivation_hook( __FILE__, 'myplugin_deactivate' );

/**
 * Activate the plugin, install version 0.1 of the table
 */
function myplugin_activate() {
	global $wpdb;
	$table_name = $wpdb->prefix . 'myplugin_table';
	$sql = "CREATE TABLE $table_name (
		id bigint(11) NOT NULL AUTO_INCREMENT,
		time datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
		`text` VARCHAR(255) DEFAULT '' NOT NULL,
		UNIQUE KEY id (id)
	);";
	require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
	dbDelta( $sql );
	update_option( 'myplugin_version', '0.1' );
}

/**
 * Deactivate the plugin, drop the table
 */
function myplugin_deactivate() {
	global $wpdb;
	$table_name = $wpdb->prefix . 'myplugin_table';
	$sql = "DROP TABLE IF EXISTS $table_name;";
	$wpdb->query( $sql );
	delete_option( 'myplugin_version' );
}

/**
 * Upgrade database to version 0.1.1
 */
function myplugin_upgrade() {
	global $wpdb;
	$table_name = $wpdb->prefix . 'myplugin_table';
	$version = get_option( 'myplugin_version' );
	if ( empty( $version ) || version_compare( $version, '0.1.1' ) < 0 ) {
		$sql = "CREATE TABLE $table_name (
			id bigint(11) NOT NULL AUTO_INCREMENT,
			time datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
			`text` VARCHAR(255) DEFAULT '' NOT NULL,
			`user_ip` int(11) DEFAULT 0,
			UNIQUE KEY `id` (`id`),
			KEY `user_ip` (`user_ip`)
		);";
		require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
		dbDelta( $sql );
		update_option( 'myplugin_version', '0.1.1' );
	}
}