SUM from two tables, sort by country and publisher - sql-server-2008

Question

I have two different sales tables and i want to SUM the quantity and FEEs for storeX and storeY from book_sales(isa), with quantity from all sales in the financial_report(xo). Im having trouble with both, and i dont know which JOIN i should use. The quantity calculation does not give any results and the fee calculation gives a number that is way to high. What is wrong here?
Please check my procedure if you have time:
ALTER PROCEDURE [dbo].[Report] #startDate VARCHAR(10),
#endDate VARCHAR(10)
AS
SELECT BB.name AS 'Publisher',
Sum(CASE
WHEN isa.report_source = 'storeX'
or isa.report_source = 'storeY' THEN
isa.quantity * xo.quantity
END) AS 'Total quantity',
Sum(CASE
WHEN isa.sales_price > 69
AND isa.report_source = 'storeX' THEN
6 * 1.25 * isa.quantity
WHEN isa.sales_price <= 69
AND isa.report_source = 'storeX' THEN
3 * 1.25 * isa.quantity
WHEN isa.sales_price <= 19
AND isa.report_source = 'storeX' THEN
1 * 1.25 * isa.quantity
WHEN isa.sales_price > 69
AND isa.report_source = 'storeY' THEN
6 * 1.25 * isa.quantity
WHEN isa.sales_price <= 69
AND isa.report_source = 'storeY' THEN
3 * 1.25 * isa.quantity
WHEN isa.sales_price <= 19
AND isa.report_source = 'storeY' THEN
1 * 1.25 * isa.quantity
WHEN xo.sales_price > 69
AND bb.country = 'NOR' THEN 6 * 1.25 * xo.quantity
WHEN xo.sales_price <= 69
AND bb.country = 'NOR' THEN 3 * 1.25 * xo.quantity
WHEN xo.sales_price > 69
AND bb.country <> 'NOR' THEN 6 * xo.quantity
WHEN xo.sales_price <= 69
AND bb.country <> 'NOR' THEN 3 * xo.quantity
END) AS 'Fee inc VAT(tot)'
FROM book_sales AS isa
INNER JOIN store AS BV
ON bv.store_id = isa.store_id
INNER JOIN financial_report AS xo
ON xo.identifiers = isa.identifiers
LEFT OUTER JOIN publisher AS BB
ON bb.publisher_id = bk.publisher_id
WHERE isa.sales_date >= CONVERT(DATETIME, #startDate, 20)
AND isa.sales_date < Dateadd(day, 1, ( CONVERT(DATETIME, #endDate, 20
) ))
GROUP BY bb.name,
bb.country

Answer 1

There are a few problems to sort out :
1- The total might be affected by NULL values, I suggest:
Sum(CASE
WHEN isa.report_source = 'storeX'
or isa.report_source = 'storeY' THEN
isnull(isa.quantity,0) * isnull(xo.quantity,0)
ELSE 0 END) AS 'Total quantity',
2- The case evaluation should be in order. For example:
WHEN isa.sales_price <= 69
AND isa.report_source = 'storeX' THEN
3 * 1.25 * isa.quantity
WHEN isa.sales_price <= 19
AND isa.report_source = 'storeX' THEN
1 * 1.25 * isa.quantity
<= 19 will never happen because it is also <= 69 and therefore the <=69 will evaluate true.
3- Cardinality between tables might be 1 to many so the values are summed multiple times when they shouldn't. You may need to select distinct or aggregate or flatten out some of the tables in the join to avoid this issue.