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Editorial Team
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Asked: 2026-06-10T06:02:34+00:00

I need to get data from multiple tables from a database and I need

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I need to get data from multiple tables from a database and I need to use 1 query. The trouble I am having is that I need to count how many tasks there are for each project and how many tasks are finished.

I got these table:
projects:

id    name        start_date           end_date             project_leader    finished
1     project_1   2012-08-01 00:00:00  2012-29-01 00:00:00  2                 0

users

id    username    password    email      status
1     user_1      pass_1      email_1    1
2     user_2      pass_2      email_2    1

user_has_project

userid   projectId
1        1

tasks

id   project  description          end_date               user  finished
1    1        test description 1   2012-29-01 00:00:00    1     1
2    1        test description 2   2012-29-01 00:00:00    1     0

So what I need to do, is make a query that should give me this result:
Wanted Result:

project_id  project_name    start_date           end_date             project_leader    finished       tasks      finished_tasks
1           project_1       2012-08-01 00:00:00  2012-29-01 00:00:00  user_2            0              2          1

I got it to work until the part where I need to count the amount of tasks that are finished. I got this query so far, but it doesn’t count the finished tasks yet. How can I do this?

Query:

SELECT projects.id,
       projects.name,
       projects.start_date,
       projects.end_date,
       projects.finished,
       users.username AS project_leader,
       COUNT(tasks.id) AS tasks
FROM projects
LEFT JOIN tasks ON (tasks.project = projects.id)
JOIN user_has_project ON (user_has_project.projectId = projects.id)
JOIN users ON (projects.project_leader = users.id)
WHERE user_has_project.userId = 1
GROUP BY projects.id
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1 Answer

  1. Editorial Team

    I’m jumping the gun a little bit here (I’ll continue contemplating in case this gut-reaction is wrong), but the trick might be to use a “null if false” evaluation inside the count() function, which is documented to only count non-null values: 

    SELECT projects.id,
       projects.name,
       projects.start_date,
       projects.end_date,
       projects.finished,
       users.username AS project_leader,
       COUNT(tasks.id) AS tasks,
       COUNT(NULLIF(tasks.finished, 0)) as finished_tasks
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