Question

我在构建查询时遇到问题，我在“未知列”上遇到错误，j.id在on子句中。

这是我目前的查询

SELECT 
    j.id,
    j.title,
    venues.name as venueName,
    ja.completed
FROM
    dbsivcmsnew.jobs AS j, 
    venues
LEFT JOIN dbsiv.job_applications AS ja ON ja.jobId = j.id
WHERE 
    j.venueId = venues.id 
    AND j.closingDate > UNIX_TIMESTAMP()
    AND j.active = 1
ORDER BY 
    j.closingDate DESC

从here我可以看到，语法是正确的。

但是，JOIN可能是不必要的，我的查询需要返回的是

SELECT 
    j.id,
    j.title,
    venues.name as venueName,
    ja.completed
FROM
    jobs AS j, 
    venues,
    dbsiv.job_applications AS ja
WHERE 
    j.venueId = venues.id 
    AND j.closingDate > UNIX_TIMESTAMP()
    AND j.active = 1
    AND ja.pin = $CurrentUsersId //This needs to optional though, if no match ja.completed should be 0
ORDER BY 
    j.closingDate DESC

是否可以在不使用连接的情况下使WHERE语句可选？

Answer 1

好吧，你为＆＃34; table join＆＃34;混合了语法，这是......不是一个好主意

只需在LEFT JOIN中添加你的附加条款即可。

SELECT 
    j.id,
    j.title,
    v.name as venueName,
    ja.completed
FROM
    jobs j
inner join venues v on v.id = j.venueID
left join dbsiv.job_applications ja on ja.jobId = j.id and ja.pin = $CurrentUsersId
WHERE 

    AND j.closingDate > UNIX_TIMESTAMP()
    AND j.active = 1
ORDER BY 
    j.closingDate DESC

Answer 2

将您的选择更改为：

SELECT 
    j.id,
    j.title,
    venues.name as venueName,
    ja.completed
FROM
    dbsivcmsnew.jobs AS j join  j.venueId = venues.id 
    venues on 
LEFT JOIN dbsiv.job_applications AS ja ON ja.jobId = j.id
WHERE 
    j.closingDate > UNIX_TIMESTAMP()
    AND j.active = 1
ORDER BY 
    j.closingDate DESC

如果您使用join，则将其用于from statement

中的所有表

Answer 3

由于您指定INNER JOIN的顺序，在连接条件下无法访问列j.id.我重新安排了订单，如下所示：

SELECT 
    j.id,
    j.title,
    venues.name as venueName,
    ja.completed
FROM    
    VENUES
INNER JOIN dbsivcmsnew.jobs AS j ON j.venueId = venues.id
LEFT JOIN dbsiv.job_applications AS ja ON ja.jobId = j.id
WHERE j.closingDate > UNIX_TIMESTAMP()
AND j.active = 1
ORDER BY J.CLOSINGDATE DESC;

从2个不同的数据库加入时出现未知的列错误

3 个答案: