4表深度mysql查找

Question

I have 4 tables - companies, projects, workers, tasks Each company has several projects, Each projects has several workers, Each worker has several tasks.

In the tasks table, there is an "estimated_cost" field. I want to view the list of all the companies, but I want it sorted by the estimated_cost of the task with the highest estimated_cost within it.

Any ideas?

Answer 1

I use MSSQL not MySQL so the syntax may not be 100%... but try this.

SELECT company.name, MAX(estimated_cost) AS HighestCost
FROM companies 
INNER JOIN projects ON projects.companyid = projects.id
INNER JOIN workers ON workers.projectid = workers.id
INNER JOIN tasks ON tasks.workerid = tasks.id
GROUP BY company.name
ORDER BY HighestCost DESC