Please copy and run following script

DECLARE @Customers TABLE (CustomerId INT)
DECLARE @Orders TABLE ( OrderId INT, CustomerId INT, OrderDate DATETIME )
DECLARE @Calls TABLE (CallId INT, CallTime DATETIME, CallToId INT, OrderId INT)
-----------------------------------------------------------------
INSERT INTO @Customers SELECT 1
INSERT INTO @Customers SELECT 2
-----------------------------------------------------------------
INSERT INTO @Orders SELECT 10, 1, DATEADD(d, -20, GETDATE())
INSERT INTO @Orders SELECT 11, 1, DATEADD(d, -10, GETDATE())
-----------------------------------------------------------------
INSERT INTO @Calls SELECT 101, DATEADD(d, -19, GETDATE()), 1, NULL
INSERT INTO @Calls SELECT 102, DATEADD(d, -17, GETDATE()), 1, NULL
INSERT INTO @Calls SELECT 103, DATEADD(d, -9, GETDATE()), 1, NULL
INSERT INTO @Calls SELECT 104, DATEADD(d, -6, GETDATE()), 1, NULL
INSERT INTO @Calls SELECT 105, DATEADD(d, -5, GETDATE()), 1, NULL
-----------------------------------------------------------------

I want to update @Calls table and need following results.

I am using the following query

UPDATE  @Calls
SET     OrderId = ( 
                    CASE 
                        WHEN (s.CallTime > e.OrderDate)
                          THEN e.OrderId
                    END                                 
                )
FROM    @Calls s INNER JOIN @Orders e   ON s.CallToId = e.CustomerId

and the result of my query is not what I need.

Requirement: As you can see there are two orders. One is on 2010-12-12 and one is on 2010-12-22. I want to update @Calls table with relevant OrderId with respect to CallTime.

In short If subsequent Orders are added, and there are further calls then we assume that a new call is associated with the most recent Order

Note: This is sample data so this is not the case that I always have two Orders. There might be 10+ Orders and 100+ calls.

Note2 I could not find good title for this question. Please change it if you think of any better.

Thanks.