public function get_lesson_completions( $period = 'current' ) {

		global $wpdb;

		$lessons = implode( ',', $this->post->get_lessons( 'ids' ) );
		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared

		// Return early for courses without any lessons.
		if ( empty( $lessons ) ) {
			return 0;
		}

		return $wpdb->get_var(
			$wpdb->prepare(
				"
			SELECT COUNT( * )
			FROM {$wpdb->prefix}lifterlms_user_postmeta
			WHERE meta_value = 'yes'
			  AND meta_key = '_is_complete'
			  AND post_id IN ( {$lessons} )
			  AND updated_date BETWEEN %s AND %s
			",
				$this->get_date( $period, 'start' ),
				$this->get_date( $period, 'end' )
			)
		);// db call ok; no-cache ok.
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared

	}