SQL - where MIN date is exactly 7 days ago

Question

I need to select only the lines where MIN date is 7 days ago. I have Customers with invoices, the invoices have due dates. I can select MIN due date of these invoices per Customer. I am now stuck as I cannot select only the Customers who are exactly 7 days overdue with their oldest invoice.

This is what I have:

select
 customerID,
 MIN(dueDate) as min_due_date
 from invoices
 where (invoiceStatus NOT IN ('PaidPosted','Cancelled'))
 and (entity = 'HQ')
 group by (customerID)

I tried adding:

and min_due_date = dateadd(day, -7, SYSDATE())

This does not work. What am I doing wrong?

Thanks.

Answer 1

Use a having clause to filter the minimum date:

select customerID, min(dueDate) as min_due_date
from invoices
where invoiceStatus not in ('PaidPosted', 'Cancelled') and
      entity = 'HQ'
group by customerID
having min(duedate) = current_date - interval '7 day';

Note that date functions are highly database specific. The above is standard SQL, but the exact syntax depends on the database you are using.

Answer 2

Thank you, Gordon, you put me on the right track! This is what eventually did the trick:

select customerID, min(dueDate) as min_due_date
from invoices
where invoiceStatus not in ('PaidPosted', 'Cancelled') and
      entity = 'HQ'
having MIN(dueDate) = trunc(sysdate) -7
group by customerID