To retrieve the Maximum Date from the record

Question

Hi All,
I am using the bleow query to retrieve the max date from the record list:
select w.wr_no,w.customer_id,w.place_id, w.entry_Date, max(app.appointment_date) as appointment_date
from work_request w , wr_appointment app
where w.wr_no=app.wr_no
and w.customer_id = '020167001'
and w.place_id = '1151667'
group by w.wr_no, w.customer_id,w.place_id, w.entry_Date;
However i am getting the as many as three rows even after using the max function. The max date comes as the last record out the three rows retrieved.
Thanks,
Mark

Answer 1

Mark Andrew wrote:
And for Sven for the above customer id and place id, i receive the below result:
WR_NO CUSTOMER_ID PLACE_ID ENTRY_DATE APPOINTMENT_DATE
1306782233 020167001 1151667 26/07/2010 29/07/2010
1387090103 020167001 1151667 26/02/2010 16/03/2010
1393896673 020167001 1151667 23/01/2011 25/01/2011
After using the rank function i will be receiving:
WR_NO CUSTOMER_ID PLACE_ID ENTRY_DATE APPOINTMENT_DATE RK
1393896673 020167001 1151667 23/01/2011 25/01/2011 1Now I get it.
In fact you want to group only on the customer (and place_id?) and get all the information from the line with the last appointment date.
Analytic functions such as RANK or ROW_NUMBER are good for this.
The select can look like this.
select * from (
   select w.wr_no,w.customer_id,w.place_id, w.entry_Date, app.appointment_date,
         row_number() over (partition by w.customer_id, w.place_id order by  app.appointment_date desc,  w.wr_no desc) rn
   from work_request w , wr_appointment app
  where w.wr_no=app.wr_no
  --and w.customer_id = '020167001'
  --and w.place_id = '1151667'
where rn = 1
;In fact I think you can do the same operation in EXCEL directly.
FIrst you need to sort the data by customer (asc), place (asc) and appointment date (desc).
Then add a column in excel that give you the line where you have a new customer id.
Assuming this new column is column H and the customerid is in column A then the function in Cell H2 would look like this.
A function like ("=A2=A1"). Copy this formular to all the other H cells.
Then add a auto filter on it and only select all the rows where the result is FALSE.
Same logic as in SQL, but done in Excel.