Between Dates

Question

Hi,
Can anyone help, I am having trouble with producing a query that looks at two dates and determines if the employee was active during certains years and months.
I have a query that outputs the employees effective start date and effective end date:
person_id effective_start_date effective_end_date
118 01-JUN-2010 31-DEC-4712
1120 01-APR-2009 01-JAN-2010
110 01-SEP-2008 31-DEC-4712
For active employees the maximum end date defaults to 31-DEC-4712.
I am trying to find out if an employee was active between Years 2007-2010 using a condition:
e.g. Querying Month = SEP-2010
effective_start_date < 01-SEP-2010 and effective_end_date >= 01-SEP-2010
How can this be acheived in the output, I would like a table that shows occurences by month as below:
person_id active_month
118 Jun-2010
118 Jul-2010
118 Aug-2010
118 Sep -2010 etc. until 2012
Can anyone help?
Thanks
I would like the results to insert a record

Answer 1

Can anyone help?Sure.
WITH my_data as (
SELECT 118 person_id,to_date('01-JUN-2010','DD-MON-YYYY') effective_start_date,to_date('31-DEC-4712','DD-MON-YYYY') effective_end_date FROM DUAL
UNION ALL
SELECT 1120 person_id,to_date('01-APR-2009','DD-MON-YYYY') effective_start_date,to_date('01-JAN-2010','DD-MON-YYYY')effective_end_date FROM DUAL
UNION ALL
SELECT 110 person_id,to_date('01-SEP-2008','DD-MON-YYYY') effective_start_date,to_date('31-DEC-4712','DD-MON-YYYY')effective_end_date FROM DUAL),
month_starts AS (
SELECT  DISTINCT DT FROM (
SELECT LAST_DAY(to_date('01-AUG-2008','DD-MON-YYYY') + (LEVEL +1))+1 AS DT
FROM DUAL
CONNECT BY LEVEL <= to_date('01-NOV-2012','DD-MON-YYYY') -  (to_date('01-AUG-2008','DD-MON-YYYY'))))
SELECT my_data.person_id,to_char(month_starts.dt,'MON-YYYY') Mt
from my_data
inner join month_starts
ON (month_starts.dt between my_data.effective_start_date and my_data.effective_end_date)
where my_data.person_id=118
order by month_starts.dt Asc;
order by month_starts.dt Asc;
PERSON_ID              MT               
118                    JUN-2010         
118                    JUL-2010         
118                    AUG-2010         
118                    SEP-2010         
118                    OCT-2010         
118                    NOV-2010         
118                    DEC-2010         
118                    JAN-2011         
118                    FEB-2011         
118                    MAR-2011         
118                    APR-2011         
118                    MAY-2011         
118                    JUN-2011         
118                    JUL-2011
....     Why "until 2012" and not 4712 ;-)
-- andy