Question

我知道此主题已经在此处讨论过，但我需要对其他问题有不同的结果。

我需要在机构名称和候选人姓氏上订购一些结果。

SELECT DISTINCT candidates.*, histories.job_title, institutions.name
FROM candidates
JOIN histories ON histories.candidate_id = candidates.id
JOIN institutions ON histories.institution_id = institutions.id
WHERE candidates.id IN (1,3,4,6)
ORDER BY institutions.name, candidates.last_name;

我的问题是目前这将返回所有候选人加入历史（当前/过去的就业），但如果我添加

AND histories.finish_date IS NULL

不会返回没有历史记录或设置完成日期的候选人。

谢谢，Alex

子查询

SELECT DISTINCT candidates.*, 
   (SELECT institution_id
        FROM histories
        WHERE histories.candidate_id = candidates.id AND histories.finish_date IS NULL
        LIMIT 1) AS job_title       
   FROM candidates
  JOIN institutions ON histories.institution_id = institutions.id
WHERE candidates.id IN (1,3,4,6)

Answer 1

尝试在历史记录表中使用左连接：

SELECT DISTINCT candidates.*, histories.job_title, institutions.name
FROM candidates
LEFT JOIN histories ON histories.candidate_id = candidates.id AND histories.finish_date IS NULL
JOIN institutions ON histories.institution_id = institutions.id
WHERE candidates.id IN (1,3,4,6)
ORDER BY institutions.name, candidates.last_name;

我无法验证这一点，你必须为我做。它应该归还所有候选人及其历史（如果有的话）。

MYSQL - 限制连接

1 个答案: