Question

在我的网站上，我有一种方法允许登录用户将文章标记为收藏，当登录文章时突出显示为保存为收藏夹，但如果用户没有收藏夹，我无法获得查询返回任何数据，我的查询有什么问题？

SELECT `job_id`, 
    COUNT(jobs.job_id) as jobs, 
    `employers`.`employer_id`, 
    `logo_small`, `logo_large`, 
    `company_name`, `job_tags`, 
    `favourite_employers`.`employer_id` AS employer 
FROM (`employers`) 
LEFT JOIN `jobs` ON `employers`.`employer_id` = `jobs`.`employer_id` 
JOIN `favourite_employers` ON `favourite_employers`.`employer_id` = `jobs`.`employer_id` 
WHERE `favourite_employers`.`user_id` = '2' 
GROUP BY `jobs`.`employer_id` 
ORDER BY `jobs`.`job_id` DESC

Answer 1

对LEFT JOIN表

使用JOIN而不是favourite_employers

Answer 2

我知道这可能看起来很愚蠢，但您是否使用;结束了查询？

Answer 3

最好看到数据库架构，但LEFT JOIN可能需要favourite_employers。

Answer 4

原因可能是因为这次加入：

JOIN `favourite_employers` ON `favourite_employers`.`employer_id` = `jobs`.`employer_id`

没有返回，因为没有收藏夹

mysql帮助...麻烦返回数据

4 个答案: