Different results in SQL based on what columns I display - sql

Question

I am trying to run a query to gather the total items on hand in our database. However it seems i'm getting incorrect data. I am selecting selecting just the amount field and summing it using joins from separate tables based on certain parameters, however if I display additional fields such as order number, and date all of a sudden im getting different data, even though those fields are being used as filters in the query. Is it because its not in the select statement? If it needs to be in the select statement is it possible to not display them?
Here are the two queries.
-- Items On Hand
select CONVERT(decimal(25, 2), SUM(tw.amount)) as 'Amt'
from [Sales Header] sh
join
(
select *
from TWAllOrders
where [Status] like 'Released'
) tw
on tw.[Order Nb] = sh.No_
join
(
select *
from OnHand
) oh
on tw.No_ = oh.[Item No_]
where sh.[Requested Delivery Date] < getdate()
HAVING SUM(tw.Quantity) <= SUM(oh.Qty)
providing a sum of 21667457.20
and with the added columns
-- Items On Hand
select CONVERT(decimal(25, 2), SUM(tw.amount)) as 'Amt', [Requested Delivery Date], sh.No_, tw.[Status]
from [Sales Header] sh
join
(
select *
from TWAllOrders
where [Status] like 'Released'
) tw
on tw.[Order Nb] = sh.No_
join
(
select *
from OnHand
) oh
on tw.No_ = oh.[Item No_]
where sh.[Requested Delivery Date] < getdate()
group by sh.[Requested Delivery Date], sh.No_, tw.[Status]
HAVING SUM(tw.Quantity) <= SUM(oh.Qty)
order by sh.[Requested Delivery Date] ASC
Providing a sum of 12319998
I'm self taught in SQL so I may be misunderstanding something obvious, thanks for the help.

Answer 1

With no sample data, I am going to have to demonstrate this in principle. In the latter query you have a GROUP BY meaning the scope of the values in the HAVING will differ, and thus the filtering from said HAVING will be different.
Let's take the following sample data:
CREATE TABLE dbo.MyTable (Grp char(1),
Quantity int,
Required int);
INSERT INTO dbo.MyTable (Grp, Quantity, [Required])
VALUES('a',2,7),
('a',14,2),
('b',4, 7),
('b',3,4),
('c',17,5);
Now we'll perform an overly simplified version of your query:
SELECT SUM(Quantity)
FROM dbo.MyTable
HAVING SUM(Quantity) > SUM(Required);
This brings back the value 40; which is the SUM of all the values in Quantity. A value is returned because the total SUM of Required is 25.
Now let's add a GROUP BY like your second query:
SELECT SUM(Quantity)
FROM dbo.MyTable
GROUP BY Grp
HAVING SUM(Quantity) > SUM(Required);
Now we have 2 rows, with the values 16 and 17 giving a total value of 33. That's because the rows where Grp have a value of 'B' are filtered out, as the SUM of Quantity is lower that Required for 'B'.
The same is happening in your data; in the grouped data you have groups where the HAVING condition isn't met, so those rows aren't returned.