ldest known order.
		$is_first_order = (int) $order->get_id() === (int) $first_order->order_id;
		// Order date has changed and next oldest is now the first order.
		$date_change = $second_order &&
			$order->get_date_created() > wc_string_to_datetime( $first_order->date_created ) &&
			wc_string_to_datetime( $second_order->date_created ) < $order->get_date_created();
		// Status has changed to an excluded status and next oldest order is now the first order.
		$status_change = $second_order &&
			in_array( $order->get_status(), $excluded_statuses, true );
		if ( $is_first_order && ( $date_change || $status_change ) ) {
			self::set_customer_first_order( $customer_id, $second_order->order_id );
			return true;
		}

		return (int) $order->get_id() !== (int) $first_order->order_id;
	}

	/**
	 * Set a customer's first order and all others to returning.
	 *
	 * @param int $customer_id Customer ID.
	 * @param int $order_id Order ID.
	 */
	protected static function set_customer_first_order( $customer_id, $order_id ) {
		global $wpdb;
		$orders_stats_table = self::get_db_table_name();

		$wpdb->query(
			$wpdb->prepare(
				// phpcs:ignore Generic.Commenting.Todo.TaskFound
				// TODO: use the %i placeholder to prepare the table name when available in the the minimum required WordPress version.
				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
				"UPDATE {$orders_stats_table} SET returning_customer = CASE WHEN order_id = %d THEN false ELSE true END WHERE customer_id = %d",
				$order_id,
				$customer_id
			)
		);
	}

	/**
	 * Initialize query objects.
	 */
	protected function initialize_queries() {
		$this->clear_all_clauses();
		unset( $this->subquery );
		$this->total_query = new SqlQuery( $this->context . '_total' );
		$this->total_query->add_sql_clause( 'from', self::get_db_table_name() );

		$this->interval_query = new SqlQuery( $this->context . '_interval' );
		$this->interval_query->add_sql_clause( 'from', self::get_db_table_name() );
		$this->interval_query->add_sql_clause( 'group_by', 'time_interval' );
	}
}