SQL Lookup in MS Access Query

Question

I have an Access Database with a table [Inventory] with following fields:

[Inventory].[Warehouse]
[Inventory].[PartNumber]

I also have a query [TransactionsQry] with following fielfd:

[TransactionsQry].[PartNumber]
[TransactionsQry].[SumofTransactions]

Now I would like to make a new query which shows all part numbers per Warehouse (from table [Inventory]) and look up related (number of) transactions in query [TransactionsQry]. Not every part number in [Inventory] has transactions yet and if so I would like to display "0".

At first I successfully tried this with a DLookup, but the result is a very slow query for very little data.

That is why I tried the following (but unsuccessfully displaying only matched part numbers and an additional error message):

SELECT 
    Inventory.Warehouse AS Warehouse, 
    TransactionsQry.PartNumber AS PartNumber, 
    TransactionsQry.SumofTransactions AS SumofTransactions
FROM Inventory 
    INNER JOIN TransactionsQry ON Inventory.PartNumber = TransactionsQry.PartNumber;

Any help with solving this issue in SQL is highly appreciated. Thanks.

Answer 1

You want to use left join rather than inner join for this. Also, table aliases make queries easier to read and write:

SELECT i.Warehouse AS Warehouse, 
       tq.PartNumber AS PartNumber, 
       nz(tq.SumofTransactions, 0) AS SumofTransactions
FROM Inventory as i LEFT JOIN
     TransactionsQry as tq
     ON i.PartNumber = tq.PartNumber;

However, I'm guessing that you really want a group by :

SELECT i.Warehouse AS Warehouse, 
       tq.PartNumber AS PartNumber, 
       nz(sum(tq.SumofTransactions), 0) AS SumofTransactions
FROM Inventory as i LEFT JOIN
     TransactionsQry as tq
     ON i.PartNumber = tq.PartNumber
GROUP BY i.Warehouse, tq.PartNumber;

Answer 2

You would be needing a LEFT JOIN based on what you need. Along with a Nz to treat Nulls as 0. Here is the corrected CODE

SELECT 
    Inventory.Warehouse AS Warehouse, 
    TransactionsQry.PartNumber AS PartNumber, 
    Nz(TransactionsQry.SumofTransactions, 0) AS SumofTransactions 
FROM 
    Inventory LEFT JOIN TransactionsQry 
ON 
    Inventory.PartNumber = TransactionsQry.PartNumber;