在进行具有相关性排序的查询时，我的排名为0

Question

我正在研究搜索算法，尝试按相关性对它们进行排名时遇到了麻烦。谁能轻轻地提供一些帮助？ $这是查询：

SELECT `listings`.*, 
       `c`.`category_name`, 
       `p`.`profile_name`, 
       CASE WHEN Lower(listings.title) IN ("pizzeria", "ristorante") THEN 1 ELSE 
       0 end 
       + CASE WHEN Lower(listings.address) IN ("pizzeria", "ristorante") THEN 1 
       ELSE 0 
       end + CASE WHEN Lower(c.category_name) IN ("pizzeria", "ristorante") THEN 
       1 ELSE 
       0 end + CASE WHEN Lower(co.province) IN ("pizzeria", "ristorante") THEN 1 
       ELSE 0 
       end             AS rank, 
       `co`.`comune`   AS `comune`, 
       `co`.`province` AS `province`, 
       `co`.`region`   AS `region`, 
       `co`.`short_code`, 
       `u`.`username` 
FROM   `listings` 
       LEFT JOIN `comune` `co` 
              ON `listings`.`id_city` = `co`.`id` 
       LEFT JOIN `aauth_users` `u` 
              ON `listings`.`id_user` = `u`.`id` 
       LEFT JOIN `categories` `c` 
              ON `listings`.`id_category` = `c`.`id` 
       LEFT JOIN `profiles` `p` 
              ON `listings`.`id_profile` = `p`.`id` 
WHERE  ( `listings`.`title` LIKE '%pizzeria%' escape '!' 
          OR `c`.`category_name` LIKE '%pizzeria%' escape '!' 
          OR `listings`.`address` LIKE '%pizzeria%' escape '!' 
          OR `co`.`province` LIKE '%pizzeria%' escape '!' ) 
        OR ( `listings`.`title` LIKE '%ristorante%' escape '!' 
              OR `c`.`category_name` LIKE '%ristorante%' escape '!' 
              OR `listings`.`address` LIKE '%ristorante%' escape '!' 
              OR `co`.`province` LIKE '%ristorante%' escape '!' ) 
ORDER  BY `rank` ASC 
LIMIT  15 

listings.title中的文本比萨店和类别名称中的ristorante应该输出[rank] => 2，但是当我打印结果数组时，它显示[rank] => 0。