Create info in new field based on sales information

[redjim]

I was trying to make a little update query that
would use some sales information to create a minimum in-stock quantity for shopassist. I don't use the % markup field, so I was
planning on putting the information there. This is the query I first made:

update invntry
set invntry."% MARKUP" =
(SELECT SUM(sales_d.Qty) QTY
FROM sales_d D, sales_h H, INVNTRY I
WHERE sales_d.Slip_Number = sales_h.Slip_Number AND I."DESCRIPTION" =
D."DESCRIPTION" AND ((sales_h."Date">='04/12/02')) and supplier = 'MAXIMA')
where supplier = 'MAXIMA'

The problem with this is that I have 3 items for this supplier:
Sales were as follows:
Item1 8
Item2 6
Item3 1

When I ran the above query, I get a value of 15 in the % markup field for
all three of the products. That is obviously wrong.

I tried the following query:

update invntry
set invntry."% MARKUP" =
(SELECT description, SUM(sales_d.Qty) QTY
FROM sales_d D, sales_h H, INVNTRY I
WHERE sales_d.Slip_Number = sales_h.Slip_Number AND I."DESCRIPTION" =
D."DESCRIPTION" AND ((sales_h."Date">='04/12/02')) and supplier = 'MAXIMA'
order by description)
where supplier = 'MAXIMA'

and I got a type mismatch error.
I assume that I got the following results of the query
Item1 8
Item2 6
Item3 1
and I couldn't put that into the % markupfield.

How can I go about making this query work so that I can put the sales per
item per "x number of days sales" into some field in the table???
Thanks for any help.