Query for all hours in a month?

Question

Hello,
I was hoping someone might be able to assist. I need to query for all the hours in a user specified date range (generally a month). For example,
a query such as:
select all hr_end from dual where start_date between '01-feb-2010' and '28-feb-2010'
that returns:
feb 01 2010 01:00
feb 01 2010 02:00
feb 01 2010 03:00
feb 28 2010 23:00
feb 28 2010 24:00
Ideally, I want to be able to run this query within a WITH clause such that I can reference the temporary table/ list of hours in a subsequent select statement quickly. Something like:
With
all_hrs_in_month AS
select .....
where start_date between '01-mar-2010' and '31-mar-2010'
I've looked around for similar questions, but have only found ones for all the 'days' in a month using level, connect by, row_num, for which I'm honestly not too familiar with and wasn't clear as to how I could modify to my needs.
Greatly appreciate your help with this request.
- j
Edited by: user12942939 on Apr 5, 2010 12:04 PM

Answer 1

Hi,
Welcome to the forum!
WITH     got_parameters  AS
     SELECT     TO_DATE ('01-mar-2010 00:00', 'dd-mon-yyyy hh24:mi')     AS start_date
     ,     TO_DATE ('31-mar-2010 23:00', 'dd-mon-yyyy hh24:mi')     AS end_date
     FROM     dual
,     all_hrs          AS
     SELECT     start_date + ( (LEVEL - 1)
                    / 24
                    )     AS hr
     FROM    got_parameters
     CONNECT BY     LEVEL <= 1 + ( 24
                               * (end_date - start_date)
SELECT       TO_CHAR (hr, 'DD-Mon-YYYY HH24:MI')     AS h
FROM       all_hrs
ORDER BY  hr
;Output:
H
01-Mar-2010 00:00
01-Mar-2010 01:00
01-Mar-2010 02:00
01-Mar-2010 03:00
31-Mar-2010 22:00
31-Mar-2010 23:00Notice that start_date and end_date don't have to span then entire month; they don't even have to be in the same month.
If you'd rather specify just one parameter (such as a single string containing the month and year):
WITH     got_parameters  AS
     SELECT     TRUNC ( TO_DATE (:p_month, 'mon-yyyy')
                , 'MONTH'
                )          AS start_date
     ,     TRUNC ( ADD_MONTHS ( TO_DATE (:p_month, 'mon-yyyy')
                             , 1
                , 'MONTH'
                )          AS end_date
     FROM     dual
,     all_hrs          AS
     SELECT     start_date + ( (LEVEL - 1)
                    / 24
                    )     AS hr
     FROM    got_parameters
     CONNECT BY     LEVEL <= ( 24          -- NOTE: Not adding 1 here
                           * (end_date - start_date)
SELECT       TO_CHAR (hr, 'DD-Mon-YYYY HH24:MI')     AS h
FROM       all_hrs
ORDER BY  hr
How It Works
SELECT  LEVEL  AS n
FROM    dual
CONNECT BY  LEVEL <= x
;Produces a result set consiting of the integers 1, 2, 3, ..., x.
There's nothing magical about the dual table; you can use any table AS LONG AS THE TABLE HAS ONLY ONE ROW .
The other examples you saw probably just added this to a starting date, to get successive days, since, in Oracle date arithmetic, dt+n is a DATE n days after dt.
Your case is slightly more complicated, because you want to add hours, not days. Since an hour is 1/24 of a day, we multiply by 24 to find how many integers to genereate, and divide by 24 when adding that number to the base date.
Edited by: Frank Kulash on Apr 5, 2010 3:07 PM