Question

I need to get top 1 record from same customer inserted within one hour. If record is inserted after one hour then don’t need that one.
Please see following table. This is just a sample of 1000s of records. I am using SQL Server 2005.

alt text http://img651.imageshack.us/img651/3990/customershavingmultiple.png

Answer 1

The idea is as follows

• Select all child orders within one hour with its minimum possible (Parent)ID. (I am assuming here that the lowest OrderID will also be the oldest OrderID).
• Join these results with the original table.
• Use these results as the basis of the update statement.

SQL Statement

UPDATE  Orders
SET     ParentOrderID = p.ParentOrderID
FROM    Orders o
        INNER JOIN (
          SELECT  ParentOrderID = MIN(o1.OrderID), OrderID = o2.OrderID
          FROM    Orders o1
                  LEFT OUTER JOIN Orders o2 ON 
                    o2.CustomerID = o1.CustomerID
                    AND o2.OrderDate > o1.OrderDate
                    AND DATEADD(hh, -1, o2.OrderDate) < o1.OrderDate
          GROUP BY o2.OrderID
        ) p ON p.OrderID = o.OrderID