Select All rows in when count(*) = count(IDField) - sql-server

Question

I have this table in SQL Server 2008.
id | TaskID | TaskHours
------------------------
0 | 25 | 1
1 | 25 | 0
2 | 24 | 1
3 | 24 | 2
4 | 24 | 2
5 | 23 | 0
I want to know how to select all by TaskID where the TaskHours all have a value > 0. I also want to select all rows by TaskID where the TaskHours have a 0 in them.
Basically I want to know if a task is completed by giving me all rows.
so Completed Tasks should show
id | TaskID | TaskHours
------------------------
2 | 24 | 1
3 | 24 | 2
4 | 24 | 2
and non completed tasks should show
id | TaskID | TaskHours
------------------------
0 | 25 | 1
1 | 25 | 0
5 | 23 | 0
I've tried
select * from tblTasks where TaskHours > 0
but I got this and I don't want 25 because it has a 0.
id | TaskID | TaskHours
------------------------
0 | 25 | 1
2 | 24 | 1
3 | 24 | 2
4 | 24 | 2
I've tried count(*) and count(Taskhours) > 0 but I couldn't get any further.
Any ideas?

Answer 1

For both queries, you may use exists logic. For the first query, consider:
SELECT t1.id, t1.TaskID, t1.TaskHours
FROM tblTasks t1
WHERE NOT EXISTS (SELECT 1 FROM tlbTasks t2
WHERE t2.TaskID = t1.TaskID AND t2.TaskHours = 0);
And for all tasks which have at least one record with zero task hours:
SELECT t1.id, t1.TaskID, t1.TaskHours
FROM tblTasks t1
WHERE EXISTS (SELECT 1 FROM tlbTasks t2
WHERE t2.TaskID = t1.TaskID AND t2.TaskHours = 0);

Answer 2

You can use CTE(Common Table expressions) together with NOT EXISTS, EXISTS clause to derive the results.
DECLARE #tasks TABLE(id int, taskid int, taskhours int)
INSERT INTO #tasks
values
(0 , 25 , 1),
(1 , 25 , 0),
(2 , 24 , 1),
(3 , 24 , 2),
(4 , 24 , 2),
(5 , 23 , 0);
;WITH CTE_TasksCompleted AS
(
SELECT DISTINCT TaskId FROM #tasks
WHERE taskhours = 0
)
-- Completed Tasks
SELECT ot.* FROM #tasks as ot
WHERE Not exists (SELECT TaskId from CTE_TasksCompleted
WHERE taskId = ot.taskId)
;WITH CTE_TasksCompleted AS
(
SELECT DISTINCT TaskId FROM #tasks
WHERE taskhours = 0
)
-- NotCompleted Tasks
SELECT ot.* FROM #tasks as ot
WHERE exists (SELECT TaskId from CTE_TasksCompleted
WHERE taskId = ot.taskId)
Completed Tasks
+----+--------+-----------+
| id | taskid | taskhours |
+----+--------+-----------+
| 2 | 24 | 1 |
| 3 | 24 | 2 |
| 4 | 24 | 2 |
+----+--------+-----------+
Not Completed Tasks
+----+--------+-----------+
| id | taskid | taskhours |
+----+--------+-----------+
| 0 | 25 | 1 |
| 1 | 25 | 0 |
| 5 | 23 | 0 |
+----+--------+-----------+