public static function get_main_search_query_sql() {
		global $wpdb;

		$args         = self::$product_query->query_vars;
		$search_terms = isset( $args['search_terms'] ) ? $args['search_terms'] : array();
		$sql          = array();

		foreach ( $search_terms as $term ) {
			// Terms prefixed with '-' should be excluded.
			$include = '-' !== substr( $term, 0, 1 );

			if ( $include ) {
				$like_op  = 'LIKE';
				$andor_op = 'OR';
			} else {
				$like_op  = 'NOT LIKE';
				$andor_op = 'AND';
				$term     = substr( $term, 1 );
			}

			$like  = '%' . $wpdb->esc_like( $term ) . '%';
			$sql[] = $wpdb->prepare( "(($wpdb->posts.post_title $like_op %s) $andor_op ($wpdb->posts.post_excerpt $like_op %s) $andor_op ($wpdb->posts.post_content $like_op %s))", $like, $like, $like ); // unprepared SQL ok.
		}

		if ( ! empty( $sql ) && ! is_user_logged_in() ) {
			$sql[] = "($wpdb->posts.post_password = '')";
		}

		return implode( ' AND ', $sql );
	}