Question

I’m trying to query my SQL database to get the number of orders made by each client within a certain date range.

I have a list of orders as follows

CustomerName       ClientID        DateOrdered
Customer No.2         10            2011-11-25
Customer No.3         11            2011-10-15
Customer No.3         11            2011-11-25

and I want to be able to find out how many orders have been made by a specific client for example between 2011-11-1 and 2011-11-30, this should result in :

CustomerName       ClientID        Number
Customer No.3         11             1
Customer No.2         10             1

So far I’ve managed to get this

SELECT CustomerName, ClientID, COUNT(*) AS Number      
FROM Orders t     
GROUP BY CustomerName, ClientID      
HAVING COUNT(*) =      
(SELECT MAX(Number)         
FROM          
(SELECT CustomerName, ClientID, COUNT(*) AS Number             
FROM Orders            
GROUP BY CustomerName, ClientID ) x       
WHERE CustomerName = t.CustomerName )

Which gives me every order the customer has ever made

CustomerName       ClientID        Number
Customer No.3         11             2
Customer No.2         10             1

Am I going about the right way to solve this or is there a simpler way which I’ve completely overlooked!

Answer 1

select CustomerName, ClientID, count(*)
from
(
    select CustomerName, ClientID
    from Orders
    where datediff(mm, DateOrdered, getdate()) <= 1
 )a
group by CustomerName, ClientID

What this does is utilize a subquery that filters the rows by the dates in a given month (that seems to be what you are looking for). Then it groups by the CustomerName and ClientID and gets the sum of their orders.