At 06:53 PM 4/11/2008, you wrote:

>Hi Set,
>
>>I don't quite grasp your structure, so it is difficult to give sound
>advice. How is COMMUNICATIONS and INCIDENT defined, what is their
>>relationship and approximately how many records are there within each
>table and for each customer?
>Just answered in reply to Helen's mail, but in short:
>
>Table Records
>Customers 15000 PK ID
>Incidents 150000 PK ID, CustomerID references Customers.ID
>Comms 1500000 PK ID, IncidentID references Incidents.ID
>
>Need to extract max date in Comms per Customer

So what you said before isn't quite correct. You have a 1:1 relationship between an Incident and a Customer, and a 1:1 relationship between a Comm and an Incident. That won't let your comms records get confused by customer.

select
i.CustomerID,
(select cus.Customer_name from Customers cus
where cus.CustomerID = i.CustomerID) as Customer,
max(c.xDate) Last_Comm_Date
from Incidents i
join Comms.c
on c.IncidentID = i.Incident_id
group by 1,2

./heLen