Question

Ok so I have a table

Tasks
--
TaskId  (unique autoinc primary)
ChildOf   (Contains task ID of parent, or 0 if top tier (no parent))

I need to write a query that selects all records with ChildOf = 0 … Simple right ?

Ok but also need to have another column returned with the results that tells how many Children each Task has …

So result would look like this …

TaskID ...  ChildOf ... countChildren
 37   ......  0   ....    3
 42   ......  0   ....    0
 99   ......  0   ....    1 

etc.... 

I know the two queries I need are something like this, but need to combine them somehow…

Select TaskId as ParentTaskId, ChildOf from Tasks where ChildOf = 0

and

Select count(TaskId) from Tasks where ChildOf = ParentTaskId

NOTE: There are only 2 tiers.. Parent and Child … No Grandchildren! So hopefully that makes it a bit less complicated.

Any help is greatly appreciated. Thanks for all the help so far!

Answer 1

Something like this should do it:

SELECT TaskId as ParentTaskId, ChildOf , 
 (SELECT count(t2.TaskId) 
  FROM Tasks t2
  WHERE t2.ChildOf = t.TaskId) as CountChildren
FROM Tasks t 
WHERE t.ChildOf = 0