Compare date ranges in two tables

Question

Hello,
I'm trying to figure out a way of comparing the range of dates between two date columns from a single row in one table, to the range of dates from multiple rows in a related table.
t1 (t1_id, absent_start_date, absent_stop_date)
t2 (t2_id, t1_id, cover_start_date, cover_end_date)
t2 has multiple rows for each row in t1
I need to select rows from t1, in which the set of days for rows in t2 do not match the set of days between absent_start_date and absent_stop_date.
For example, assume this row in t1:
1, '10/08/2007', '15/08/2007'
The set of days would be 10/08/07,11/08/07,12/08/07,13/08/07,14/08/07,15/08/07
and these rows in t2
1, 1, '10/08/2007', '11/08/2007'
2, 1, '12/08/2007', '12/08/2007'
3, 1, '14/08/2007', '15/08/2007'
The set of days would be 10/08/07,11/08/07,12/08/07,14/08/07,15/08/07
In this case, the related rows in t2 do not cover the same date range as the master row in t1, and so I need to select this row from t1 somehow.
Any ideas anyone?
Thanks.

Answer 1

I am not sure about the exact output you want, but the next query will give you all gaps in the periods, so the presence of a row in this output may be enough?
SQL> create table t1
  2  as
  3  select 1 t1_id, date '2007-08-10' absent_start_date, date '2007-08-15' absent_stop_date from dual union all
  4  select 2, date '2007-09-01', date '2007-09-10' from dual
  5  /
Tabel is aangemaakt.
SQL> create table t2
  2  as
  3  select 1 t2_id, 1 t1_id, date '2007-08-10' cover_start_date, date '2007-08-11' cover_stop_date from dual union all
  4  select 2, 1, date '2007-08-12', date '2007-08-12' from dual union all
  5  select 3, 1, date '2007-08-14', date '2007-08-15' from dual union all
  6  select 4, 2, date '2007-09-03', date '2007-09-05' from dual union all
  7  select 5, 2, date '2007-09-07', date '2007-09-08' from dual
  8  /
Tabel is aangemaakt.
SQL> select  *
  2    from ( select t2.t1_id
  3                , lag(t2.end_date+1,1,t1.absent_start_date) over (partition by t2.t1_id order by t2.start_date) gap_start_date
  4                , t2.start_date-1 gap_end_date
  5             from t1
  6                , ( select t1_id
  7                         , cover_start_date start_date
  8                         , cover_stop_date end_date
  9                      from t2
10                     union all
11                    select t1_id
12                         , absent_stop_date+1
13                         , absent_stop_date+1
14                      from t1
15                  ) t2
16            where t1.t1_id = t2.t1_id
17         )
18   where gap_start_date <= gap_end_date
19   order by t1_id
20       , gap_start_date
21  /
                                 T1_ID GAP_START_DATE      GAP_END_DATE
                                     1 13-08-2007 00:00:00 13-08-2007 00:00:00
                                     2 01-09-2007 00:00:00 02-09-2007 00:00:00
                                     2 06-09-2007 00:00:00 06-09-2007 00:00:00
                                     2 09-09-2007 00:00:00 10-09-2007 00:00:00
4 rijen zijn geselecteerd.Regards,
Rob.