mysql查询的问题

我有以下疑问

SELECT 
  `c`.`id` AS `confession_id`,
  `c`.`account_id` AS `confession_author_id`,
  `c`.`confession_text`,
  `c`.`anonymous`,
  `c`.`total_likes`,
  `c`.`total_comments`,
  `c`.`creation_date`,
  `a`.`username`,
  `col`.`name` AS `college`,
  `col`.`avatar_url`,
  `cll`.`deleted` AS `tacc_exists` 
FROM
  `confessions` AS `c` 
  LEFT JOIN `accounts` AS `a` 
    ON `a`.`id` = `c`.`account_id` 
  LEFT JOIN `colleges` AS `col` 
    ON `col`.`id` = `c`.`college_id` 
  LEFT JOIN `confession_likes_log` AS `cll` 
    ON `cll`.`confession_id` = `c`.`id` 
    AND `cll`.`account_id` = :taccd_user 
    AND `c`.`college_id` IN ('9') 
ORDER BY `c`.`id` DESC 
LIMIT 10 

假设它根据提供的学院id从指定学院中选择条目

---

尽管出于某种原因，即使学院id不是指定的id，它也会选择条目。我在计算如何使用左连接执行and子句时遇到了问题，因此我可能没有正确设置查询的格式。

这是您的

where

子句：

              FROM `confessions` AS `c` LEFT JOIN
                   `colleges` AS `col`
                    ON `col`.`id` = `c`.`college_id` LEFT JOIN
                   `confession_likes_log` AS `cll`
                    ON `cll`.`confession_id` = `c`.`id` AND
                       `cll`.`account_id` = :taccd_user AND
                        `c`.`college_id` in ('9')

left join

的工作方式是：在

on

子句中运行测试。如果第一个表中的给定行不匹配，则包含右表中具有

NULL

值的行。猜猜看。这甚至适用于第一个表中的条件

因此，（'9'）中的过滤器

c.college\u id没有按照您的想法进行操作。您需要将其移动到

where`子句：

              FROM `confessions` AS `c` LEFT JOIN
                   `colleges` AS `col`
                    ON `col`.`id` = `c`.`college_id` LEFT JOIN
                   `confession_likes_log` AS `cll`
                    ON `cll`.`confession_id` = `c`.`id` AND
                       `cll`.`account_id` = :taccd_user
              WHERE `c`.`college_id` in ('9')

              FROM `confessions` AS `c` LEFT JOIN
                   `colleges` AS `col`
                    ON `col`.`id` = `c`.`college_id` LEFT JOIN
                   `confession_likes_log` AS `cll`
                    ON `cll`.`confession_id` = `c`.`id` AND
                       `cll`.`account_id` = :taccd_user
              WHERE `c`.`college_id` in ('9')