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Home > Forums > Programmers > DBMS Packages > -General database discussion Forum

Simple SQL grouping question

Read More Threads Like This One

mattjp (Programmer)

23 Sep 08 13:51

Hi, I'm relatively green at SQL queries, and I was wondering what the best way to construct a t-sql query on this data:

table: activitylog
fields: serial#, starttime, stoptime, activity

'serial' is non-unique, 'serial' + 'starttime' is unique. I need a query that will return, for each serial number, the row with the most recent (greatest) 'starttime' timestamp.

For example, for this table:

SN#     start    stop   act
1234    12:00    12:15  a
1235    13:34    13.45  a
1234    13:50    14:02  b

I need to be able to get:
SN#     start    stop   act
1235    13:34    13.45  a
1234    13:50    14:02  b

What is the best way to do this? Group By doesn't work this way, and I don't think it can be done with a join. Thanks for the help.

genomon (Programmer)

23 Sep 08 16:34

Check the FAQs at forum183: Microsoft SQL Server: Programming.

"Don't be irreplaceable. If you can't be replaced, you can't be promoted."

r937 (TechnicalUser)

23 Sep 08 23:01

CODE

SELECT "serial#"
     , starttime
     , stoptime
     , activity
  FROM activitylog
INNER
  JOIN ( SELECT "serial#"
              , MAX(starttime) AS maxtime
           FROM activitylog
         GROUP
             BY "serial#" ) AS m
    ON m."serial#" = activitylog."serial#"
   AND m.maxtime = activitylog.starttime

r937.com | rudy.ca

mattjp (Programmer)

24 Sep 08 8:07

Thanks--you solved my problem completely!

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