Create a Dates View

Question

Hi gurus, my first question here.:-)
My DBA gave me a table with only one date column say Table1.Date. Its in the format of Date and say it is = 7/23/2012.
Now i have to create my own Reporting View(which is used for reporting) based on that date column like below:
It should be a column with values in the following format =
2012-07
2012-06
2012-05 etc....upto
2010-01
So i started out my creating like this:
select
to_char(Table1.Date,'yyyy-mm')
from Table1
Union
select SUBSTR(to_char(Table1.Date,'yyyy-mm'), 1,5)||TO_CHAR(SUBSTR(to_char(Table1.Date,'yyyy-mm'), 6, 2)-1)
from
Table1
Union
select SUBSTR(to_char(Table1.Date,'yyyy-mm'), 1,5)||TO_CHAR(SUBSTR(to_char(Table1.Date,'yyyy-mm'), 6, 2)-2)
from
Table1
etc
.and so on till i get 2010-01.
I was wondering, there has to be a better way to do this. Any sugguestions please?
Thanks,
Brawn

Answer 1

Hi,
Welcome to the forum!
Whenever you have a problem, please post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) from all tables involved.
Also post the results you want from that data, and an explanation of how you get those results from that data, with specific examples.
Always say which version of Oracle you're using, e.g. 10.2.0.4.0.
See the forum FAQ {message:id=9360002}
An example of some sample data in your case might be:
CREATE TABLE  table1
(       date_column     DATE
INSERT INTO table1 (date_column) VALUES (TO_DATE ( '7/23/2012', 'MM/DD/YYYY'));
INSERT INTO table1 (date_column) VALUES (TO_DATE ( '7/20/2012', 'MM/DD/YYYY'));
INSERT INTO table1 (date_column) VALUES (TO_DATE ( '7/30/2012', 'MM/DD/YYYY'));
INSERT INTO table1 (date_column) VALUES (TO_DATE ('04/05/2012', 'MM/DD/YYYY'));
COMMIT;Do you want a view that has one row per month, starting with the earliest month in table1, and continuing through the latest month in table1?
If so:
CREATE OR REPLACE VIEW       all_months
AS
SELECT     ADD_MONTHS ( last_month
             , 1 - LEVEL
             )               AS a_month
FROM    (
         SELECT  TRUNC (MIN (date_column), 'MONTH')     AS first_month
         ,         TRUNC (MAX (date_column), 'MONTH')     AS last_month
         FROM    table1
CONNECT BY     LEVEL <= 1 + MONTHS_BETWEEN ( last_month
                                        , first_month
;Given the data I posted above, this query:
SELECT       TO_CHAR (a_month, 'YYYY-MM')     AS formatted_month
FROM       all_months
ORDER BY  a_month
;produces this output:
FORMATTED_MONTH
2012-04
2012-05
2012-06
2012-07Notice that the view contains row for May and June, even though the table doesn't have any data for those months.
Edited by: Frank Kulash on Jul 30, 2012 4:53 PM
Added sample data.