DROP PROCEDURE IF EXISTS w_unique;

 DELIMITER /w/

 CREATE PROCEDURE w_unique()

 BEGIN

   DECLARE done INT DEFAULT FALSE;

   DECLARE w_wmax INT;

   DECLARE w_grab_review_url VARCHAR(256);

   DECLARE wcur CURSOR FOR SELECT MAX(grab_tab_review_pk) AS  wmax, grab_review_url FROM grab_tab_review WHERE LENGTH(grab_review_url)>0 GROUP BY grab_review_url;

   DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

   OPEN wcur;

   read_loop: LOOP

     FETCH wcur INTO w_wmax, w_grab_review_url;

     IF done THEN LEAVE read_loop;

     END IF;

         SET @wtmp = CONCAT('DELETE FROM grab_tab_review WHERE grab_tab_review_pk!=',w_wmax,' AND grab_review_url="',w_grab_review_url,'"');

         PREPARE  stmt FROM @wtmp ;

         EXECUTE  stmt ;

         DROP PREPARE stmt;

   END LOOP;

   CLOSE wcur;

 END/w/

 DELIMITER;

 CALL w_unique();

 DROP PROCEDURE IF EXISTS w_self_update;

 DELIMITER /w/

 CREATE PROCEDURE w_self_update(w_arr  VARCHAR(36))

 BEGIN

   DECLARE done INT DEFAULT FALSE;

   DECLARE w_grab_tab_review_pk INT;

   DECLARE w_grab_review_url VARCHAR(256);

   DECLARE wcur CURSOR FOR SELECT grab_tab_review_pk, grab_review_url FROM grab_tab_review WHERE LENGTH(grab_review_url)>0;

   DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

   OPEN wcur;

   read_loop: LOOP

     FETCH wcur INTO w_grab_tab_review_pk, w_grab_review_url,w_countrycode;

     IF done THEN LEAVE read_loop;

     END IF;

         SET @w=LOCATE(w_arr,w_grab_review_url);

         SET @wb=LOCATE('/ref=',w_grab_review_url);

         SET @wstr=SUBSTR(w_grab_review_url,@w + LENGTH(w_arr),@wb - @w - LENGTH(w_arr));

         SET @wtmp = CONCAT('UPDATE grab_tab_review ',' SET amz_review_id="',@wstr,'" WHERE grab_tab_review_pk=',w_grab_tab_review_pk);

         PREPARE  stmt FROM @wtmp ;

         IF @w>0 THEN EXECUTE  stmt ;

     END IF;

         DROP PREPARE stmt;

   END LOOP;

   CLOSE wcur;

 END/w/

 DELIMITER;

 CALL w_self_update('-reviews/');

 CALL w_self_update('-review/');

 https://www.amazon.com.mx/review/R1OR2BGFHA44LE/ref=cm_cr_dp_title?ie=UTF8&ASIN=B0196IK0OM&channel=detail-glance&nodeID=9482690011&store=software

 https://www.amazon.com.mx/gp/customer-reviews/R1OR2BGFHA44LE/ref=cm_cr_dp_title?ie=UTF8&ASIN=B0196IK0OM&channel=detail-glance&nodeID=9482690011&store=software

 ===>

 R1OR2BGFHA44LE

 SELECT grab_review_url FROM grab_tab_review WHERE grab_tab_review_pk=123456;

 SELECT

     SUBSTR(

         (

             SELECT

                 grab_review_url

             FROM

                 grab_tab_review

             WHERE

                 grab_tab_review_pk = 123456

         ),

         LOCATE(

             '-reviews/',

             (

                 SELECT

                     grab_review_url

                 FROM

                     grab_tab_review

                 WHERE

                     grab_tab_review_pk = 123456

             )

         ) + LENGTH('-reviews/'),

         LOCATE(

             '/ref=',

             (

                 SELECT

                     grab_review_url

                 FROM

                     grab_tab_review

                 WHERE

                     grab_tab_review_pk = 123456

             )

         ) - LOCATE(

             '-reviews/',

             (

                 SELECT

                     grab_review_url

                 FROM

                     grab_tab_review

                 WHERE

                     grab_tab_review_pk = 123456

             )

         ) - LENGTH('-reviews/')

     );