Subject Re: SubQuery Help
Author E. D. Epperson Jr
I'd recommend using a left join with table alias.

Example

Select
  a.Project_PK
, SUM(b.cost) AS Sum_of_Cost
, SUM(b.estimate_cost) AS Sum_of_Estimated_Cost
, SUM(c.quantity) AS Sum_of_Quantity
, SUM(c.estimate_quantity) AS Sum_of_Estimated_Quantity
FROM Projects a
LEFT JOIN Cost b ON a.project_pk = b.project_pk
LEFT JOIN Quantity c ON a.project_pk = c.project_pk

--
Dixon Epperson