dynamic copyright shortcode

Add start year and current year with a shortcode

// Add Shortcode
function wcd_focussports_copyright_year() {

	global $wpdb;
	
	$copyright_dates = $wpdb->get_results("
	
	SELECT
	
	YEAR(min(post_date_gmt)) AS firstdate,
	
	YEAR(max(post_date_gmt)) AS lastdate
	
	FROM
	
	$wpdb->posts
	
	WHERE
	
	post_status = 'publish'
	
	");
	
	$output = '';
	
	if($copyright_dates) {
	
	$copyright = $copyright_dates[0]->firstdate;
	
	if($copyright_dates[0]->firstdate != $copyright_dates[0]->lastdate) {
	
	$copyright .= '-' . $copyright_dates[0]->lastdate;
	
	}
	
	$output = $copyright;
	
	}
	return $output;

}
add_shortcode( 'copyright', 'wcd_focussports_copyright_year' );