SQL: Query 2 tables to get latest date for each record

Question

I have two tables that I want to query Customer and Service

Customer table

    cnum       lastName        Address       Phone        Comments      

     2         McKenzie        Main Street   1234567898   None
     3         Stevenson       South Street  1225448844   None
     4         Adams           North Street  1234545454   None

Service

     IncidentNum     cnum      serviceDate      status       category      LastUpdated

     x1               2        02-21-2013       Closed       Repair        02-21-2013
     c2               2        05-12-2013       Open         Installation  05-13-2013
     d2               3        05-01-2013       Closed       Repair        05-05-2013
     f2               4        05-12-2013       Open         Repair        05-12-2013

Basically what I want to do is display the records with latest update for each customer record, regardless if the status is Closed or Open.

Final:

    cnum    lastName     Address        Phone        Category       Last Service
     2      McKenzie     Main Street    1234567898   Installation   05-13-2013
     3      Stevenson    South Street   1225448844   Repair         05-05-2013
     4      Adams        North Street   1234545454   Repair         05-12-2013

Im using OLEDB, this is for my project in VB. Any input would be appreciated. Thank you in advance!

Answer 1

this is very simple.. see you have to join these two tables on * cnum *and then top of that you can put condition for latest/maximum servicedate..

You can use following query for the same task -

select customer.cnum,
       customer.lastname,
       customer.address,
       customer.phone,
       service.category,
       service.servicedate 
  from customer,service
 where customer.cnum = service.cnum
   and service.servicedate = ( select max(serviceDate) from service service2
                                where service2.cnum = customer.cnum)

I hope this is what you are looking for..

Edit : Editing query to display the customer info which is not present in service table

select customer.cnum,
       customer.lastname,
       customer.address,
       customer.phone,
       service.category,
       service.servicedate 
  from customer left outer join service on (customer.cnum = service.cnum)
   where (service.servicedate = ( select max(serviceDate) from service service2
                                where service2.cnum = customer.cnum)
          or service.cnum is null)

Answer 2

Can you please try this?

select c.cnum, c.lastname, c.address,
c.phone, s.category, s.servicedate 
from customer c,service s
where c.cnum = s.cnum
group by c.cnum
having s.LastUpdated = max(s.LastUpdated)

Answer 3

select distinct customer.cnum,customer.lastname,customer.address,customer.phone,
service.category,
MAX(lastupdated)as lastservice from service,customer where service.cnum=customer.cnum
and service.servicedate = ( select max(serviceDate) from service service2
                            where service2.cnum = customer.cnum)
group by customer.cnum,customer.lastname,customer.address,customer.phone,
service.category

I hope this is what you are looking for. I tested it and it gives the exact output you mentioned in the question.