Varchar to Datetime conversion and selecting latest datead records

Question

Hi:
I've a table as below:
ActionDate|Status|Name
23/10/2012|Block|James
24/10/2012|Open|James
25/10/2012|Block|James
20/09/2012|Block|Tanya
17/09/2012|Block|Fox
18/09/2012|Open|Fox
27/08/2012|Block|Martin
27/08/2012|Open|Martin
Desired Output is as follows:
ActionDate|Status|Name
25/10/2012|Block|James
20/09/2012|Block|Tanya
Select those records only which has Block staus on most recent date. It will also eliminate those which has Open status on the same date.
One more problem is the ActionDate field is actually Varchar2 type and there are mismatch as well. For example: some of those are in MM/DD/YYYY and
some are in DD/MM/YYYY
So, how can I convert these strings into formated date and make the desired output in a single query. Please let me know.
Thanks/Tanvir

Answer 1

Hi, Tanvir,
853856 wrote:
Hi:
I've a table as below:
ActionDate|Status|Name
23/10/2012|Block|James
24/10/2012|Open|James
25/10/2012|Block|James
20/09/2012|Block|Tanya
17/09/2012|Block|Fox
18/09/2012|Open|Fox
27/08/2012|Block|Martin
27/08/2012|Open|MartinWhenever you have a problem, please post CREATE TABLE and INSERT statements for your sample data.
Desired Output is as follows:
ActionDate|Status|Name
25/10/2012|Block|James
20/09/2012|Block|TanyaSee the forum FAQ {message:id=9360002} for how to format the ouptut on this site (among other things).
Select those records only which has Block staus on most recent date. It will also eliminate those which has Open status on the same date.
One more problem is the ActionDate field is actually Varchar2 type That's not a very good idea. This problem shows just one of the many reasons why you should always use DATE columns for date information.
and there are mismatch as well. For example: some of those are in MM/DD/YYYY and
some are in DD/MM/YYYYThe you have no way of knowing if '01/12/2012' means January 12 or December 1. The query below arbitrarily assumes that will be December 1.
So, how can I convert these strings into formated date and make the desired output in a single query. Please let me know.
Thanks/TanvirHere's one way:
WITH     got_real_actiondate     AS
     SELECT     TO_DATE ( actiondate
               , CASE
                         WHEN  SUBSTR (actiondate, 4, 2)     <= '12'
                     THEN  'MM/DD/YYYY'
                     ELSE  'DD/MM/YYYY'
                 END
               )     AS real_actiondate
     ,     status
     ,     name
     FROM     a_table
,     got_r_num     AS
     SELECT     real_actiondate
     ,     status
     ,     name
     ,     ROW_NUMBER () OVER ( PARTITION BY  name
                               ORDER BY          real_actindate     DESC
                         ,                CASE
                                          WHEN  status = 'Open'
                                     THEN  1
                                     ELSE  2
                                      END
                       ) AS r_num
     FROM    got_real_actiondate
SELECT     real_actiondate
,     status
,     name
FROM     got_r_num
WHERE     r_num     = 1
AND     status     != 'Open'
;This assumes that actiondate is in either 'DD/MM/YYYY' or 'MM/DD/YYYY' format, which is very optimistic. If you sometimes have other formats as well, and/or text that can't be interpreted as a date in any format, then see {message:id=4252963}
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
In the case of a DML operation (such as INSERT) the sample data should show what the tables are like before the DML, and the results will be the contents of the changed table(s) after the DML.
Explain, using specific examples, how you get those results from that data.
Always say what version of Oracle you're using (e.g. 11.2.0.2.0).
See the forum FAQ {message:id=9360002}