SQL Server UNION or JOIN - sql-server

Question

I am having a bit of problem with JOIN or UNION? Would you help me solve this?
Here is my story.
I have two tables: tbl_inventory and tbl_delivery.
Here is the scenario. Each week I have to match a delivery and an inventory record. For example: on week 1 I have to show, the delivery and inventory for a specific product.
Inventory Date | Week # |Product |inventory qty | delivery qty
----------------------------------------------------------------------------
2018/02/12 | 7 |cheesecake | 30 | 25 |
It is fine I can do that now. The problem arise when I have no delivery or no inventory for that week? Here is my desired output:
Inventory Date | Week # |Product |inventory qty | delivery qty
----------------------------------------------------------------------------
2018/02/12 | 7 |cheesecake | NULL | 25 |
OR
Inventory Date | Week # |Product |inventory qty | delivery qty
----------------------------------------------------------------------------
2018/02/12 | 7 |cheesecake | 30 | NULL |
Would you help me achieve that? Here is my code
select a.CustCode,
b.Material,
b.Qty as deliveryQty,
d.Qty as inventoryQty
from BigEMerchandiser.dbo.tbl_Delivery_H as a
left join BigEMerchandiser.dbo.tbl_Delivery_D as b
on a.TransCtr = b.TransCtr
left join BigEMerchandiser.dbo.tbl_Inventory_H as c
on datepart(wk, a.DtRcv) = datepart(wk, c.DtRcv)
left join BigEMerchandiser.dbo.tbl_Inventory_D as d
on c.TransCtr = d.TransCtr
left join BigEMasterData.dbo.tbl_Materials as e
on b.Material = e.ExtMatGrp
UNION ALL
select a.CustCode,
b.Material,
d.Qty as deliveryQty,
b.Qty as inventoryQty
from BigEMerchandiser.dbo.tbl_Inventory_H as a
left join BigEMerchandiser.dbo.tbl_Inventory_D as b
on a.TransCtr = b.TransCtr
left join BigEMerchandiser.dbo.tbl_Delivery_H as c
on datepart(wk, a.DtRcv) = datepart(wk, c.DtRcv)
left join BigEMerchandiser.dbo.tbl_Delivery_D as d
on c.TransCtr = d.TransCtr
left join BigEMasterData.dbo.tbl_Materials as e
on b.Material = e.ExtMatGrp
I have switched from using joins and union. But still I get the same result.
Here is my inventory table result:
Here is my delivery table result:
Here is the result of my query:
As we can see, there is only one inventory but it still shows 30 on every delivery. I understand that I have used join that is why. Hope you can help me with understand UNIONs and JOIN here. Hope I explained myself clearly. Thankyou. All you suggestions are appreciated.
EDIT
Here is my new query it s outputting what I want. my problem now is how can I add there where statement? for a specific date range:
select a.CustCode,
b.Material,
b.Qty as deliveryQty,
NULL as inventoryQty
from BigEMerchandiser.dbo.tbl_Delivery_H as a
left join BigEMerchandiser.dbo.tbl_Delivery_D as b
on a.TransCtr = b.TransCtr
left join BigEMasterData.dbo.tbl_Materials as e
on b.Material = e.ExtMatGrp
UNION
select v.CustCode,
b.Material,
NULL as deliveryQty,
b.Qty as inventoryQty
from BigEMerchandiser.dbo.tbl_Inventory_H as v
left join BigEMerchandiser.dbo.tbl_Inventory_D as b
on v.TransCtr = b.TransCtr
left join BigEMasterData.dbo.tbl_Materials as e
on b.Material = e.ExtMatGrp
Thanks a lot!

Answer 1

I suspect the problem is UNION which prevents you from seeing your joins result in duplication. You should use UNION ALL, and correct your joins to include Material.
E.g. something like:
left join BigEMerchandiser.dbo.tbl_Inventory_D as d
on c.TransCtr = d.TransCtr
and c.Material = b.Material
How your tables are connected is not immediately clear, but the point is you are looking for a TransCtr in your inventory. TransCtr = 89 has an inventory of 30, it's just the wrong material.