wp_should_upgrade_global_tables example

global $wp_current_db_version, $wpdb;

    if ( $wp_current_db_version < 15093 ) {
        populate_roles_300();
    }

    if ( $wp_current_db_version < 14139 && is_multisite() && is_main_site() && ! defined( 'MULTISITE' ) && get_site_option( 'siteurl' ) === false ) {
        add_site_option( 'siteurl', '' );
    }

    // 3.0 screen options key name changes.     if ( wp_should_upgrade_global_tables() ) {
        $sql    = "DELETE FROM $wpdb->usermeta WHERE meta_key LIKE %s OR meta_key LIKE %s OR meta_key LIKE %s OR meta_key LIKE %s OR meta_key LIKE %s OR meta_key LIKE %s OR meta_key = 'manageedittagscolumnshidden' OR meta_key = 'managecategoriescolumnshidden' OR meta_key = 'manageedit-tagscolumnshidden' OR meta_key = 'manageeditcolumnshidden' OR meta_key = 'categories_per_page' OR meta_key = 'edit_tags_per_page'";