UNION WHERE

w条件语句的作用域。

 SELECT
     *
 FROM
     (
         SELECT
             asin,
             LOWER(country) AS country
         FROM
             grab_amzreviews_asins
         UNION DISTINCT
             SELECT
                 asin,
                 LOWER(country) AS country
             FROM
                 grab_amzsimilar_seller_asins
             UNION DISTINCT
                 SELECT
                     asin,
                     LOWER(country) AS country
                 FROM
                     grab_amzlisting
     ) AS w
 WHERE
     CONCAT(asin, country) NOT IN (
         SELECT
             CONCAT(asin, LOWER(country))
         FROM
             minerasinlist
     ) ;

 SELECT
     asin,
     country
 FROM
     grab_amzreviews_asins
 UNION DISTINCT
 SELECT
         asin,
         country
     FROM
         grab_amzsimilar_seller_asins
     UNION DISTINCT
 SELECT
             asin,
             country
         FROM
             grab_amzlisting
 WHERE
             CONCAT(asin, LOWER(country)) NOT IN (
                 SELECT
                     CONCAT(asin, LOWER(country))
                 FROM
                     amzasin
             );