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Message Posted: Fri, 09 Feb 2007 @ 19:23:45 GMT


     
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Subj:   Re: ROWNUM CONVERSION FOR TERADATA
 
From:   Curley, David

In your example, since selecting from dual with no where clause always returns one row, rownum - 1 will be 0 and the whole add_months business isn't needed.

So:

     select date;
     select current_timestamp;

Depending on whether or not you need the time component.

The general answer to rownum is to add row_number() over (order by <something or other>) and wrap another query around that. Not that you'd ever need to do this, but something like

     select top 10 add_months(calendar_date, -(rownum-1) )
     from (select row_number() over (order by calendar_date) rownum,
           t.calendar_date
           from date_dim t) x

(This query will fail if it happens to return rows where the add_months calculation is outside the range of valid dates.)

By the way, if you're going to use add_months, be aware that Teradata handles the last day of the month differently than Oracle:

Oracle:

     SELECT add_months('28-feb-2007',1) from dual;
     31-Mar-2007

TD:

     select add_months('2007-02-28',1);
     03/28/2007

Dave



     
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