Inner Join without repeating value, keeping the rows of the first table - sql

Question

I have a table with the discount for each invoice. For example:
Invoice Number|Discount
------------------------
1 | 3
2 | 5
3 | 6
I need to pull these discounts to the invoice lines table (because they only apply to the total of the invoice, not to a particular line). At the same time I cannot lose any line.
Example: If the invoice 1 has 5 lines, I need all lines to show up (the 5 lines of the invoice), but I want the discount only once (for example, the first line would be enough).
Expected:
Invoice Number|Discount
------------------------
1 | 3
1 | null
1 | null
1 | null
1 | null
If I have an Invoice table, and a InvoiceLines table that can be joined by the invoice number in both tables, how can I get the result that I need?
I tried this query without success:
Select
ROW_NUMBER() over(order by v.num_fra)as Rank,
l.*,
v.ctdrap_div as discount
from ffac_vta v --(invoicetable)
join ffac_hla l --(invoice lines table)
ON v.num_fra = l.num_fra
Can you help me?

Answer 1

Here is another way to do this...Basically, your sub query pulls the line item info - and gets the row number (partitioned by order number). Then, you LEFT OUTER JOIN that subset to the table with the discount value ONLY when the row number = 1. This approach doesn't require a CASE statement since the LEFT OUTER JOIN will give you NULL values for all row numbers above 1.
SELECT Sub.*,
V.ctdrap_div AS [Discount]
FROM
(
SELECT *,
ROW_NUMBER() OVER(PARTITION BY v.num_fra ORDER BY v.num_fra) AS [Row Number]
FROM ffac_hla L
) Sub
LEFT OUTER JOIN ffac_vta V
ON v.num_fra = Sub.num_fra
AND Sub.[Row Number] = 1

Answer 2

It seems like you should be able to just change your join to a left join.
Select
ROW_NUMBER() over(order by v.num_fra)as Rank,
l.*,
v.ctdrap_div as discount
from ffac_vta v --(invoicetable)
left join ffac_hla l --(invoice lines table)
ON v.num_fra = l.num_fra

Answer 3

You will need to use the key of your lines table or something to order your rows. Something like this. Also, do we have ROW_NUMBER() in SQL-Server-2008?
SELECT T.num_fra,
CASE WHEN T.rank = 1 THEN T.Discount
ELSE NULL AS Discount
FROM
(
Select
ROW_NUMBER() over(PARTITION BY v.num_fra ORDER BY <<ADD THE KEY OF INVOICE LINES HERE>>)as Rank,
l.*,
v.ctdrap_div as discount
from ffac_vta v --(invoicetable)
join ffac_hla l --(invoice lines table)
ON v.num_fra = l.num_fra
) AS T

Answer 4

Change to
;WITH cte AS (SELECT DENSE_RANK() over(order by v.num_fra)as Rank,
num_fra,
l.*,
v.ctdrap_div as discount
FROM ffac_vta v --(invoicetable)
JOIN ffac_hla l --(invoice lines table)
ON v.num_fra = l.num_fra
)
SELECT num_fra
, CASE WHEN Rank = 1 THEN discount ELSE 0 END
, *
FROM cte;

Answer 5

I think you could use left join...
For more information about join, you can see this web site : https://www.quora.com/SQL-What-is-the-difference-between-various-types-of-joins
difference between join image
I hope this help you

Answer 6

Try this:
select i.InvoiceID,Discount
from invoicedetail i
left join invoicediscount id on i.invoiceID=id.invoiceid and i.linenumber=1