@select(
        " select
            product_id,
            product_name,
            product_price,
            product_image,
            product_url
          from
            product
          where
            valid_flag = '1' "
        @condition(
                   (not (null product_name))
                   " and
                       product_name like :product_name")
        @condition(
                   (and (not (null price_low))
                        (not (null price_high)))
                   " and
                       product_price between :price_low and :price_high")
        " order by
            product_id
          limit :limit ")
(defsql fetch-product (product_name price_low price_high limit))

;; ->

(defun fetch-product (&key product_name price_low price_high limit)
  (let* ((sql (format NIL "~A~A~A~A"
                      "select product_id...."
                      (if (not (null product_name))
                          " and product_name like :product_name "
                          "")
                      (if (and (not (null price_low))
                               (not (null price_high)))
                          " and product_price between :price_low and :price_high"
                          "")
                      " order by product_id limit :limit "))
         (query (prepare *db* sql))
         (result (execute query (list :product_name product_name :price_low price_low :price_high price_high :limit limit))))
    (fetch-all result)))