TSQL: Join tables based on criteria - sql

Question

The resultset I am aiming to receive is this:
My table structure is like:
The INVOICE table has INVTYPE column which defines whether the invoice is a sales invoice or a purchase invoice by holding 101 for sale and 201 for purchase.
My query will use a where statement to also filter down the STOCK table to a particular STOCKCODE.
I am trying to filter out products (STOCK) with a STOCKCODE = "XYZ"
If I run
SELECT *
FROM STOCK
WHERE STOCKCODE = 'XYZ'
I get 152 results. So I have 152 products with a STOCKCODE of 'XYZ' for sure..
My problem is when I try to join these tables. For simplicity, I have only tried to get INVTYPE 101 to keep it simple but my desired outcome is still with the 201.
I have tried joins and subqueries such as:
SELECT
S.STOCKNO, S.STOCKNAME, ISNULL(SUM(IIT.QTYSOLD), 0) AS QTY,
ISNULL(SUM(IIT.TOTAL), 0) AS TOTAL
FROM
STOCK S
LEFT JOIN
INVOICE_ITEM IIT ON S.STOCKID = IIT.STOCKID
LEFT JOIN
INVOICE INV ON IIT.INVID = INV.INVID
WHERE
S.STOCKCODE = 'XYZ' AND INV.TRANSTYPE = 101
GROUP BY
S.STOCKNO, S.STOCKNAME
This query returns 122 results. So I know that there are 30 items in the stock table that have not been sold, which I need to show them in the resultset with 0 (zero) in the relevant columns.
I also tried this:
SELECT
S.STOCKNO, S.STOCKNAME,
(SELECT ISNULL(SUM(TOTAL), 0)
FROM INVOICE_ITEM IIT
WHERE IIT.STOCKID = S.STOCKID) AS TOTAL,
(SELECT ISNULL(SUM(QTYSOLD), 0)
FROM INVOICE_ITEM IIT
WHERE IIT.STOCKID = S.STOCKID) AS QTY
FROM
STOCK S
WHERE
S.STOCKCODE = 'XYZ'
This query return the full 152 results because I did not filter by INVTYPE it returned the items which were purchased as well.
I am using SQL Server 2014
So my question is how can I achieve my desired resultset? and what am I doing wrong with my joins?
Thanks

Answer 1

You need a conditional aggregation
SELECT S.STOCKNO,
S.STOCKNAME,
ISNULL(SUM(CASE WHEN INV.TRANSTYPE = 201 THEN IIT.TOTAL END), 0) AS TOTAL_PURCHASED,
ISNULL(SUM(CASE WHEN INV.TRANSTYPE = 101 THEN IIT.TOTAL END), 0) AS TOTAL_SOLD,
ISNULL(SUM(CASE WHEN INV.TRANSTYPE = 201 THEN IIT.QTYSOLD END),0) AS QTY_PURCHASED,
ISNULL(SUM(CASE WHEN INV.TRANSTYPE = 101 THEN IIT.QTYSOLD END),0) AS QTY_SOLD
FROM STOCK S
LEFT JOIN INVOICE_ITEM IIT ON S.STOCKID = IIT.STOCKID
LEFT JOIN INVOICE INV ON IIT.INVID= INV.INVID
WHERE S.STOCKCODE= 'XYZ'
GROUP BY S.STOCKNO, S.STOCKNAME

Answer 2

since you are not joining your inner tables (INVOICE_ITEM) with their primary key this is an expected behavior.
you either need to use INVITEMID column for your join, you need to add STOCKID and INVID together.
SELECT ISNULL(SUM(TOTAL),0) FROM INVOICE_ITEM IIT
WHERE IIT.STOCKID = S.STOCKID and IIT.INVID = INV.INVID

Answer 3

For performance, it is tempting to try:
select s.stockno, s.stockname,
coalesce(i.total_purchased, 0) as total_purchased,
coalesce(i.total_sold, 0) as total_sold,
coalesce(i.qty_purchased, 0) as qty_purchased,
coalesce(i.qty_sold, 0) as qty_sold
from stock s outer apply
(select sum(case when i.transtype = 201 then ii.total end) as total_purchased,
sum(case when i.transtype = 101 then ii.total end) as total_sold,
sum(case when i.transtype = 201 then ii.qtysold end) as qty_purchased,
sum(case when i.transtype = 101 then ii.qtysold end) as qty_sold
from invoice_item ii join
invoice i
on ii.invid = i.invid
where s.stockid = ii.stockid
) i
where stockcode = 'XYZ'