从表中获取最大日期

Question

Hopefully this is a simple one. I have a table of sent messages and a customer table. I am trying to get the date of the last message sent to a customer, but I am having a nightmare with it and can't work out what's up!!

In english: Get me the last date the customer received where the last date is greater than DateX and less than DateY.

In my SQL: (Msaccess)

SELECT 
  Max(outgoingmessages.outgoingmessagedatetime), 
  outgoingmessages.outgoingmessagecustomerID 
FROM 
  outgoingmessages 
  inner join customers on customers.customerid = 
                          outgoingmessages.outgoingmessagecustomerid 
WHERE  
  (outgoingmessages.outgoingmessagedatetime>#20/Oct/2012# 
  and 
  outgoingmessages.outgoingmessagedatetime < #02/Nov/2012# )
  and 
  outgoingmessages.outgoingmessagecustomerID NOT IN (
    SELECT incomingMessageCustomerID from incomingmessages
  ) 
GROUP BY 
  outgoingmessages.outgoingmessagecustomerID; 

I know that customerid=32 has had a message sent on 05/11, yet the query seems to be ignoring this and showing an old date of his. I literally just need to get the customerID and the date of their last message.

any ideas?!

================ UPDATE

I think the statement would work if I could say "WHERE MAX(outgoingmessagetime) BETWEEN date1 and date2)... but I cannot use the MAX date. Maybe I need a sub query?

Answer 1

Why not ... ?

SELECT Top 1 o.outgoingmessagedatetime, o.outgoingmessagecustomerID 
FROM outgoingmessages o
WHERE  o.outgoingmessagedatetime between #2012/10/02# And #2012/11/02#
ORDER BY o.outgoingmessagedatetime Desc

Note that this will not include messages sent after 2nd November. To include messages up to 5th November, say

WHERE  o.outgoingmessagedatetime between #2012/10/02# And #2012/11/05#

Re Comment

SELECT  o.outgoingmessagecustomerID, Max(o.outgoingmessagedatetime)
FROM outgoingmessages o
WHERE  o.outgoingmessagedatetime between #2012/10/02# And #2012/11/02#
AND o.outgoingmessagecustomerID NOT IN (
    SELECT outgoingmessagecustomerID FROM outgoingmessages 
    WHERE outgoingmessagedatetime > #2012/11/02#)
GROUP BY o.outgoingmessagecustomerID 

Answer 2

How about this, at first I didn't think the customers table was required but it looks as though you may only want to show records that match customers in that table so I've gone for this approach:

SELECT A.MaxDT, A.outgoingmessagecustomerID
FROM
(SELECT Max(O.outgoingmessagedatetime) AS MaxDT, O.outgoingmessagecustomerID
FROM outgoingmessages AS O
WHERE O.outgoingmessagedatetime BETWEEN >#10/21/2012# AND Date()-7
AND O.outgoingmessagecustomerID NOT IN (SELECT incomingMessageCustomerID FROM imcomingmessages)
GROUP BY O.outgoingmessagecustomerID) AS A, customers AS C
WHERE A.outgoingmessagecustomerID = C.customerID

This carries out the MAX calculation in a derived table and then just links the results back against the customer table

Ps: I wish your field names were shorter ^_^