Look at data in one date range and count from another date range - sql-server

Question

I'm stuck on a query where I am trying to get information on just customers that are newly acquired during a certain date range.
I had need to get a list of customers who placed their first order (of all time) in the first 6 months of the year. I then need to get total of their invoices, first invoice date, last invoice date, and count of orders for just the last 6 months.
I used a HAVING clause to ensure that I am just looking at customers that placed their first order in that 6 month period, but since we are past that period now, the total invoice info and order count information would include orders placed after this time. I considered including a restriction in the HAVING clause for the 'last invoice date', but then I am eliminating customers whose first order date was in the 6 month block, but also ordered after that. I'm not sure what to do next and am not having luck finding similar questions. Here is what I have so far:
SELECT c.customer, MAX(c.name) AS Name,
SUM(
CASE WHEN im.debit = 0
THEN im.amount * -1
ELSE im.amount
END
) AS TotalInvoiceAmount,
MIN(
im.date) AS FirstInvoiceDate,
MAX(
im.date) AS LastInvoiceDate,
COUNT(DISTINCT om.[order]) AS OrderCount
FROM invoicem im
INNER JOIN customer c ON im.customer = c.customer
FULL JOIN orderm om ON im.customer = om.customer
WHERE im.amount <> 0
GROUP BY c.customer
HAVING MIN(im.date) BETWEEN '01-01-2015' AND '06-30-2015'
ORDER BY c.customer

Answer 1

You can put the first 6 months qualification as a subquery. This would also work as a CTE
declare #startDate date = dateadd(month,-6,getdate())
SELECT c.customer, MAX(c.name) AS Name,
SUM(
CASE WHEN im.debit = 0
THEN im.amount * -1
ELSE im.amount
END
) AS TotalInvoiceAmount,
MIN(
im.date) AS FirstInvoiceDate,
MAX(
im.date) AS LastInvoiceDate,
COUNT(DISTINCT om.[order]) AS OrderCount
FROM invoice im
INNER JOIN (SELECT customer from invoice
GROUP BY customer
HAVING MIN(date) BETWEEN '01-01-2015'
AND '06-30-2015') im2
ON im.customer = im2.customer
INNER JOIN customer c ON im.customer = c.customer
FULL JOIN orderm om ON im.customer = om.customer
WHERE im.amount <> 0
AND im.date >= #startdate
GROUP BY c.customer
ORDER BY c.customer