访问2016查询

Question

I need some help with creating a query. This is an inventory application where Product1 is moved from location A to location B and then to location C. Location B should then have zero inventory for Product1. I have a table that stores all the movements as follows:

Movements (
    ProductName,
    QtyMoved,
    LocationFrom,
    LocationTo
)

Two entries might be:

ProductName | QtyMoved | LocationFrom | LocationTo
------------+----------+---------------------------
"Product1"  |      500 | "LocationA"  | "LocationB"
"Product1"  |      500 | "LocationB"  | "LocationC"

This query lists the above entries:

SELECT
    ProductName, QtyMoved, LocationFrom, LocationTo    
FROM
    Movements
WHERE
    LocationFrom = 'LocationB'
    OR
    LocationTo = 'locationB';

What I want is to calculate and list the total Qty in 'locationB' for 'Product1', (which would be zero, in this case).

I would like the datasheet view of the query to show 3 columns, ProductName , QtyMoved and 'LocationB' . I believe what I need is an expression like:

(total qty of Product1 in locationFrom for locationB) minus (total qty of Product1 in locationTo for locationB).  

Perhaps this would be easier if I was to create a report instead of a query. Any suggestions would be appreciated.

Answer 1

I would make a UNION query to add the moves into a location and subtract the moves out of a location - sommething like

Select ProductName, LocationTo as Location, QtyMoved as Balance from Movements
Union All Select ProductName, LocationFrom, -QtyMoved from Movements

After you save this query, you can use it as the source for a 2nd query to get the balances, something like

Select ProductName, Location, Sum(Balance) as Balance from [Movements Summary]