SQL Server Multiple count dates subselect in same query - count

Question

I'm trying to figure out a way to pull Order Counts per customer id as well as date of first and last order within a date range from an Orders table where each order has both a buyer_id and seller_id. The Orders table contains OrderNumber, Buyer_ID, Seller_ID, OpenDate, ClosedDate. I can run the following queries individually to achieve my goals, but I would like to have everything in the same query if possible.
Order_Table:
OrderNumber, Buyer_ID, Seller_ID, OpenDate, ClosedDate
Buyer_ID Orders:
select Buyer_ID, COUNT(*)as BuyerOrders
from
(
select Buyer_ID
from Orders
where OpenDate between #StartDate and #EndDate
)
a
group by Buyer_ID
Seller_ID Orders:
select Seller_ID, COUNT(*)as SellerOrders
from
(
select Seller_ID
from Orders
where OpenDate between #StartDate and #EndDate
)
a
group by Seller_ID
Dates of First and Last Order within that range: ??
Any input is greatly appreciated!
Since the result is a union and the same customer_id may have an entry as both buyer and seller, how can I put the information in the same row? My first attempt was to create a temporary table from the result of the Union, but I'm drawing a blank on how to display Buyer OrderCount, Seller OrderCount etc on the same row for each Customer_ID in the resulting table.

Answer 1

select 'Buyer' as Type,
Buyer_ID ID,
Count(*) OrderCount,
Min(OpenDate) FirstOrder,
Max(OpenDate) LastOrder
from Orders
where OpenDate between #StartDate and #EndDate
group by Buyer_ID
union
select 'Seller',
Seller_ID,
Count(*),
Min(OpenDate) FirstOrder,
Max(OpenDate) LastOrder
from Orders
where OpenDate between #StartDate and #EndDate
group by Seller_ID
[EDIT] Yes, a little bit of a cheek accepting my answer, then un-accepting it and changing the question! Anyway, try the following:
;with BuyerFirst (Buyer_ID, RowNum, BuyerCount, OrderID, OpenDate)
As
(select Buyer_ID,
ROW_NUMBER() over (partition by Buyer_ID order by OpenDate, OrderID) as RowNum,
count(*) over (partition by Buyer_ID) As BuyerCount,
OrderID,
OpenDate
from Orders
where OpenDate between #StartDate and #EndDate),
BuyerLast (Buyer_ID, RowNum, OrderID, OpenDate)
As
(select Buyer_ID,
ROW_NUMBER() over (partition by Buyer_ID order by OpenDate Desc, OrderID Desc) as RowNum,
OrderID,
OpenDate
from Orders
where OpenDate between #StartDate and #EndDate),
SellerFirst (Seller_ID, RowNum, SellerCount, OrderID, OpenDate)
As
(select Seller_ID,
ROW_NUMBER() over (partition by Seller_ID order by OpenDate, OrderID) as RowNum,
count(*) over (partition by Buyer_ID) As SellerCount,
OrderID,
OpenDate
from Orders
where OpenDate between #StartDate and #EndDate),
SellerLast (Seller_ID, RowNum, OrderID, OpenDate)
As
(select Seller_ID,
ROW_NUMBER() over (partition by Seller_ID order by OpenDate Desc, OrderID Desc) as RowNum,
OrderID,
OpenDate
from Orders
where OpenDate between #StartDate and #EndDate)
select c.*,
bf.BuyerCount,
bf.OpenDate As BuyerFirstOrderDate,
bf.OrderID As BuyerFirstOrderID,
bl.OpenDate As BuyerLastOrderDate,
bl.OrderID As BuyerLastOrderID,
sf.SellerCount,
sf.OpenDate As SellerFirstOrderDate,
sf.OrderID As SellerFirstOrderID,
sl.OpenDate As SellerLastOrderDate,
sl.OrderID As SellerLastOrderID
from Customers c
left join BuyerFirst bf on c.CustomerID = bf.Buyer_ID and bf.RowNum = 1
left join SellerFirst sf on c.CustomerID = sf.Seller_ID and sf.RowNum = 1
left join BuyerLast bl on c.CustomerID = bl.Buyer_ID and bl.RowNum = 1
left join SellerLast sl on c.CustomerID = sl.Seller_ID and sl.RowNum = 1