Oracle - How to repeat query for every year/month/week

Question

I've made a query to get the rows from my chosen columns where the date is 2018 December:

SELECT myColumn1, myColumn2 
FROM MyTable
WHERE to_char(myColumn_DATE, 'YYYY/MM') = '2018/12'

This is quite simple and I can now use these rows to create some further logic. However what if I need to repeat this for every month in a given year, or even every week?

I'm exporting the query results into separate excel tables, so I guess I would have to manually check the correct date intervals every time and can't aggregate the data for a whole year/month/etc. Isn't there some PL/SQL approach to avoid this tedious repetition?

Answer 1

Assume you're on a day from December 2018, and your aim is to populate the table MyTable2 through the data from the table MyTable .

Firstly, let's create MyTable2 without data :

create table MyTable2 as
select myColumn1, myColumn2 
  from MyTable
 where 1 = 9;

and then create a procedure by which populate MyTable2 on the last day of every month

create or replace procedure pr_populate_Mytable2 is
begin
   insert into MyTable2
   select myColumn1, myColumn2 
     from MyTable
    where to_char(myColumn_DATE, 'YYYY/MM') = to_char(sysdate,'YYYY/MM');
 commit;
end;

by calling the procedure from a dbms_scheduler as

declare
    v_job_name varchar2(32) := 'jb_populate_Mytable2';
begin  
    dbms_scheduler.create_job(
        job_name => v_job_name,
        job_type => 'STORED_PROCEDURE',
        job_action => 'pr_populate_Mytable2', 
        start_date => to_date('31-12-2018 20:00:00', 'dd-mm-yyyy hh24:mi:ss'),
        repeat_interval => 'FREQ=MONTHLY; BYMONTHDAY=-1; BYHOUR=21;',
        auto_drop => false,
        comments => 'Populates our table on the last day of every month at 21 o''clock ');

    dbms_scheduler.enable(v_job_name);    
end;

starts at 8pm on the last day of december, and repeats on every upcoming last days of the months at 9pm in the future.

Answer 2

You can use the CONNECT BY LEVEL <= trick to generate rows, and then use a combination of date functions to generate the relevant dates.

--Months for the current year.
select add_months(trunc(sysdate, 'year'), level-1) the_month
from dual
connect by level <= 12;

THE_MONTH
---------
2019-01-01
2019-02-01
2019-03-01
2019-04-01
2019-05-01
2019-06-01
2019-07-01
2019-08-01
2019-09-01
2019-10-01
2019-11-01
2019-12-01

Then create an inline view with that query, and join it to the main table:

select *
from
(
    --Months for the current year.
    select add_months(trunc(sysdate, 'year'), level-1) the_month
    from dual
    connect by level <= 12
) months
left join mytable
    on months.the_month = trunc(mycolumn_date, 'month');