Question

A Project has multiple Tasks, which has multiple Assignments

Projects (1-n) -> Tasks (1-n) -> Assignments

A field on the Tasks table is Planned Hours.

A field on the Assignments table is Assigned Hours.

How do I get the Planned Hours and Assigned Hours for all Projects in a single query?

Answer 1

select p.ProjectID, t.PlannedHoursSum, a.AssignedHoursSum
from Projects p
inner join (
    select ProjectID, sum(PlannedHours) as PlannedHoursSum
    from Tasks
    group by ProjectID
) t on p.ProjectID = t.ProjectID
inner join (
    select t.ProjectID, sum(AssignedHours) as AssignedHoursSum
    from Tasks t
    inner join Assignments a on t.TaskID = a.TaskID
    group by t.ProjectID
) a on p.ProjectID = a.ProjectID