带有查询和分组依据的 SQL Sum

Question

I have 2 tables:

like this and would like to count bill on tblsoinvoiceheader with sum on sub query by condition on ProductCode = Discount-1000

What kind of query should I have?

Answer 1

To prepare data in tblsoinvoiceheader we need to use such query:

select TransactionDate, 
       count(*) CountOfBill, 
       sum(InvoiceAmountWithTax) InvoiceAmountWithTax 
from tblsoinvoiceheader
group by TransactionDate

and then join it with result of below query:

select (-1)*LineAmountWithTax
from tblsoinvoiceitem
where ProductCode = 'Discount-1000'

Summing up:

select * from (
    select (-1)*LineAmountWithTax
    from tblsoinvoiceitem
    where ProductCode = 'Discount-1000'
-- i used cross join because you didn't specify joining condition and it looks like you want to 
-- join all recrods
) a cross join (
    select TransactionDate, 
           count(*) CountOfBill, 
           sum(InvoiceAmountWithTax) InvoiceAmountWithTax 
    from tblsoinvoiceheader
    group by TransactionDate
) b

Answer 2

If you have at most one DISCOUNT line per invoice, then you can use:

SELECT h.TransactionDate,
       COUNT(*) AS CountOfBill,
       SUM(h.InvoiceAmountWithTax) AS InvoiceAmountWithTax,
       SUM(CASE WHEN i.Remark = 'Discount' THEN -i.LineAmountWithTax END) AS Discount
FROM tblsoinvoiceheader h LEFT JOIN
     tblsoinvoiceitem i
     ON i.DocNo = h.DocNo AND
        i.Remark = 'Discount'
GROUP BY h.TransactionDate;

If you can have multiple discounts per doc, then you need to pre-aggregate.