SQL SUM columns from different tables - sql

Question

Good Afternoon,
I currently have the query:
SELECT erp_user.login,
SUM(invoice_header.invoice_amount) as 'Invoices Billed'
FROM erp_user
LEFT JOIN order_header ON erp_user.erp_user_id = order_header.req_by
LEFT JOIN invoice_instruct_header ON order_header.order_id = invoice_instruct_header.order_id
LEFT JOIN invoice_header ON invoice_instruct_header.instruct_id = invoice_header.instruct_no
WHERE erp_user.supervisor_id IS NOT NULL AND user_id_type = 'I' AND erp_user.company_id IS NOT NULL AND erp_user.is_active = 1
GROUP BY erp_user.login
It gives me a list of total billing in our system by employee where the employee is signed to a job on the job header.
I would love to add the total amount of open PO's to this query so I added:
SELECT erp_user.login, SUM(invoice_header.invoice_amount) as 'Invoices Billed', sum(po_header.po_amount) AS "Open PO's"
FROM erp_user
LEFT JOIN order_header ON erp_user.erp_user_id = order_header.req_by
LEFT JOIN invoice_instruct_header ON order_header.order_id = invoice_instruct_header.order_id
LEFT JOIN invoice_header ON invoice_instruct_header.instruct_id = invoice_header.instruct_no
LEFT JOIN po_header ON order_header.order_id = po_header.order_id
WHERE erp_user.supervisor_id IS NOT NULL AND user_id_type = 'I' AND erp_user.company_id IS NOT NULL AND erp_user.is_active = 1 AND po_header.status = 1
GROUP BY erp_user.login
ORDER BY "Open PO's"
That query gives me numbers in my Open PO's column, but they are incorrect and I'm at the point now where I can't figure out how to troubleshoot this.
Can someone please point me in the right direction? I don't mind doing the work, just need a pointer. Thanks!

Answer 1

Please be aware of conbination of Left join and Where clause.
SELECT erp_user.login
, SUM(invoice_header.invoice_amount) as 'Invoices Billed'
, sum(CASE WHEN po_header.status = 1 THEN po_header.po_amount ELSE 0 END) AS "Open PO's"
FROM erp_user
LEFT JOIN order_header ON erp_user.erp_user_id = order_header.req_by
LEFT JOIN invoice_instruct_header ON order_header.order_id = invoice_instruct_header.order_id
LEFT JOIN invoice_header ON invoice_instruct_header.instruct_id = invoice_header.instruct_no
LEFT JOIN po_header ON order_header.order_id = po_header.order_id
WHERE erp_user.supervisor_id IS NOT NULL
AND user_id_type = 'I'
AND erp_user.company_id IS NOT NULL
AND erp_user.is_active = 1
GROUP BY erp_user.login
ORDER BY "Open PO's";

Answer 2

If po_header joins to order_header, then in your original query it would be repeating each po_header for each invoice_header as well (leading to the incorrect calculation).
You could use outer apply() like so:
select
erp_user.login
, [Invoices Billed] = sum(invoice_header.invoice_amount)
, x.[Open POs]
from erp_user
left join order_header
on erp_user.erp_user_id = order_header.req_by
left join invoice_instruct_header
on order_header.order_id = invoice_instruct_header.order_id
left join invoice_header
on invoice_instruct_header.instruct_id = invoice_header.instruct_no
outer apply (
select
[Open POs] = sum(po_header.po_amount)
from po_header p
inner join order_header oh
on oh.order_id = p.order_id
where oh.req_by = erp_user.erp_user_id
) x
where erp_user.supervisor_id is not null
and erp_user.company_id is not null
and erp_user.is_active = 1
and user_id_type = 'I'
group by erp_user.login