MySQL左连接与另一个带有传递变量的表

Question

I have 2 tables named projects and tracklines Every project can have multiple tracklines.

I have an SQL statement that will loop through my projects, but I want to be able to JOIN the trackline table with only 1 row. What I want to do is get all tracklines that are part of a project, order them based on more than one field and do a LIMIT 1 on it so that I have one trackline which I'm joining with my project.

This is what I have so far:

SELECT Project.* FROM `project` AS `Project`
LEFT JOIN (
    SELECT *
    FROM `trackline`
    WHERE `trk_deleted` = '0'
    ORDER BY `trk_state`, `trk_status`
    LIMIT 1
) t ON t.`trk_project` = `prj_id`
ORDER BY `prj_name`

The problem is that I am not getting the trk_state and trk_status values in my outer query.

I was thinking that my subquery could have WHERE trk_project = prd_id but I am not sure how to get that to happen.

Answer 1

You need to pull values from that derived table as well:

SELECT Project.*, t.*
FROM ...

right now it's retrieving ONLY the fields from the Project table.