MySQL Join from multiple tables with GROUP_CONCAT

Question

I am trying to select data from 3 separate tables, where 2 of those contains multiple rows of data. The sql query i am using is this, but i am experiencing that when i run it, if either taskdependees or tasksdependencies have zero result, the whole task is not showing.

SELECT t.*, GROUP_CONCAT(a.DependenciesId) as DiesId, GROUP_CONCAT(b.DependeesId) as DeesId FROM tasks t JOIN tasksdependencies a ON a.TasksId=t.TasksId JOIN taskdependees b ON b.TasksId=t.TasksId GROUP BY t.TasksId

What am I doing wrong in this query?

try a left join instead of a join

Mike Furlender
– Mike Furlender

2014-05-08 15:53:37 +00:00
Commented May 8, 2014 at 15:53 — Mike Furlender
– Mike Furlender, Commented May 8, 2014 at 15:53

M Khalid Junaid · Accepted Answer · 2014-05-08 15:53:39Z

2

Use LEFT JOIN , inner join will give row if there is association is present in both tables while left will return the rows from left table even if they are not associated

SELECT t.*, GROUP_CONCAT(a.DependenciesId) as DiesId,
 GROUP_CONCAT(b.DependeesId) as DeesId 
FROM tasks t
LEFT JOIN tasksdependencies a ON a.TasksId=t.TasksId
LEFT JOIN taskdependees b ON b.TasksId=t.TasksId 
GROUP BY t.TasksId

answered May 8, 2014 at 15:53

M Khalid Junaid

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1 Comment

P.Davide Over a year ago

very usefull! i was posting a question like this and I found the answer, really thank you :-)

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