mysql - SELECT IF 查询

Question

我有简单的查询：

SELECT max(`id`) as `name_id` , LEFT(`name`,LENGTH(`name`)-2) AS `name`, `status` 
 FROM `users`
WHERE `site` = 1
  AND `category` = 'some'

我只需要选择那些，其中supp== YES

SELECT `model`.`supp`
  FROM `model`, `users`
 WHERE `users`.`name_id` = `name_id_from_the_first_query`
   AND `model`.`model_id` = `users`.`model_id`;

因此，只有当第二个为当前 ID 返回 YES 时，我才需要第一个查询的返回值。

Answer 1

尝试，

SELECT  max(a.`id`) as `name_id` , 
        LEFT(`name`,LENGTH(a.`name`)-2) AS `name`, 
        a.`status`
FROM    `model` a 
        INNER JOIN `users` b
            ON a.`model_id` = b.`model_id`
WHERE    a.`site` = 1 AND
         a.`category` = 'some' AND
         b.`supp` = 'YES'
GROUP BY a.`name`, a.`status`

Answer 2

试试这个查询：

SELECT max(`id`) as `name_id` , LEFT(`name`, LENGTH(`name`)-2) AS `name`
       , `status` 
 FROM `users` 
     JOIN `model` 
       ON `model`.`model_id` = `users`.`model_id`
    WHERE `site` = 1 AND `category` = 'some'
      AND `model`.`supp` = 'YES';

Answer 3

在这里，您还有另一个选择：

SELECT max(`id`) as `name_id` , LEFT(`name`,LENGTH(`name`)-2) AS `name`, `status` 
 FROM `users`
WHERE `site` = 1
  AND `category` = 'some'
  AND id IN (SELECT `model_id`
               FROM `model`
              WHERE `supp` = 'YES'
             )
GROUP BY `name`, `status`;

Answer 4

SELECT max(`id`) as `name_id` , LEFT(`name`, 
LENGTH(`name`)-2) AS `name`, `status` 
FROM `users` WHERE `site` = 1 AND `category` = 'some'
     and EXISTS
     ( 
       SELECT `model`.`supp` FROM `model` 
          WHERE `model`.`model_id` = `users`.`model_id`
                 and `model`.`supp`='Yes'
      )