How to select dates from dual, but with joined data?
If you have denormalised date it's quite simple:
with bas as (
select 1 id_other_table, to_date('2020-01-05', 'YYYY-MM-DD') date_from, to_date('2020-01-06', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 1 id_other_table, to_date('2020-01-06', 'YYYY-MM-DD') date_from, to_date('2020-01-07', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 1 id_other_table, to_date('2020-01-07', 'YYYY-MM-DD') date_from, to_date('2020-01-08', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 1 id_other_table, to_date('2020-01-10', 'YYYY-MM-DD') date_from, to_date('2020-01-11', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 1 id_other_table, to_date('2020-01-11', 'YYYY-MM-DD') date_from, to_date('2020-01-12', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 1 id_other_table, to_date('2020-01-12', 'YYYY-MM-DD') date_from, to_date('2020-01-13', 'YYYY-MM-DD') date_to, 'hello' some_info from dual
union all select 2 id_other_table, to_date('2020-01-10', 'YYYY-MM-DD') date_from, to_date('2020-01-11', 'YYYY-MM-DD') date_to, 'my' some_info from dual
union all select 2 id_other_table, to_date('2020-01-11', 'YYYY-MM-DD') date_from, to_date('2020-01-12', 'YYYY-MM-DD') date_to, 'my' some_info from dual
union all select 2 id_other_table, to_date('2020-01-12', 'YYYY-MM-DD') date_from, to_date('2020-01-13', 'YYYY-MM-DD') date_to, 'my' some_info from dual
union all select 3 id_other_table, to_date('2020-01-20', 'YYYY-MM-DD') date_from, to_date('2020-01-21', 'YYYY-MM-DD') date_to, 'friend' some_info from dual
union all select 3 id_other_table, to_date('2020-01-21', 'YYYY-MM-DD') date_from, to_date('2020-01-22', 'YYYY-MM-DD') date_to, 'friend' some_info from dual
union all select 3 id_other_table, to_date('2020-01-22', 'YYYY-MM-DD') date_from, to_date('2020-01-23', 'YYYY-MM-DD') date_to, 'friend' some_info from dual)
, ad as (select trunc(sysdate,'YYYY') -1 + level all_dates from dual connect by level <= 31)
select distinct some_info,all_dates from bas,ad where (some_info,all_dates) not in (select some_info,date_from from bas)
If you have longer date ranges or mind of the time the query needs another solution is helpful. But that is harder to debug. Because it's quite hard to get the orange time slot
Select whole range using connect by generator. Join your table partitioned by id.
select date_from, nvl(date_to, date_from +1) date_to, id_othertable, some_info
from (
select date '2020-01-01' + level - 1 as date_from
from dual
connect by level <= date '2020-01-31' - date '2020-01-01' ) gen
natural left join some_dates partition by (id_othertable)
sqlfiddle
If you want the dates per id that are not in the database then you can use the LEAD analytic function:
WITH dates ( id, date_from, date_to ) AS (
SELECT id_othertable,
DATE '2020-01-01',
MIN( date_from )
FROM some_dates
WHERE date_to > DATE '2020-01-01'
AND date_from < ADD_MONTHS( DATE '2020-01-01', 1 )
GROUP BY id_othertable
UNION ALL
SELECT id_othertable,
date_to,
LEAD( date_from, 1, ADD_MONTHS( DATE '2020-01-01', 1 ) )
OVER ( PARTITION BY id_othertable ORDER BY date_from )
FROM some_dates
WHERE date_to > DATE '2020-01-01'
AND date_from < ADD_MONTHS( DATE '2020-01-01', 1 )
)
SELECT id,
date_from,
date_to
FROM dates
WHERE date_from < date_to
ORDER BY id, date_from;
so for the test data:
CREATE TABLE some_dates ( id_othertable, date_from, date_to, some_info ) AS
SELECT 1, DATE '2020-01-05', DATE '2020-01-06', 'hello1' FROM DUAL UNION ALL
SELECT 1, DATE '2020-01-06', DATE '2020-01-07', 'hello2' FROM DUAL UNION ALL
SELECT 1, DATE '2020-01-07', DATE '2020-01-08', 'hello3' FROM DUAL UNION ALL
SELECT 1, DATE '2020-01-10', DATE '2020-01-13', 'hello4' FROM DUAL UNION ALL
SELECT 2, DATE '2020-01-10', DATE '2020-01-13', 'my' FROM DUAL UNION ALL
SELECT 3, DATE '2020-01-20', DATE '2020-01-23', 'friend' FROM DUAL UNION ALL
SELECT 4, DATE '2019-12-31', DATE '2020-01-05', 'before' FROM DUAL UNION ALL
SELECT 4, DATE '2020-01-30', DATE '2020-02-02', 'after' FROM DUAL UNION ALL
SELECT 5, DATE '2019-12-31', DATE '2020-01-10', 'only_before' FROM DUAL UNION ALL
SELECT 6, DATE '2020-01-15', DATE '2020-02-01', 'only_after' FROM DUAL UNION ALL
SELECT 7, DATE '2019-12-31', DATE '2020-02-01', 'exlude_all' FROM DUAL;
this outputs:
ID | DATE_FROM | DATE_TO -: | :--------- | :--------- 1 | 2020-01-01 | 2020-01-05 1 | 2020-01-08 | 2020-01-10 1 | 2020-01-13 | 2020-02-01 2 | 2020-01-01 | 2020-01-10 2 | 2020-01-13 | 2020-02-01 3 | 2020-01-01 | 2020-01-20 3 | 2020-01-23 | 2020-02-01 4 | 2020-01-05 | 2020-01-30 5 | 2020-01-10 | 2020-02-01 6 | 2020-01-01 | 2020-01-15
db<>fiddle here
If you want the days before then filter on:
WHERE day_from = DATE '2020-01-01'
and, similarly, if you want the days after then filter on:
WHERE day_to = ADD_MONTHS( DATE '2020-01-01', 1 )
If you want to specify the start date and number of months duration then use named bind parameters:
WITH dates ( id, date_from, date_to ) AS (
SELECT id_othertable,
:start_date,
MIN( date_from )
FROM some_dates
WHERE date_to > :start_date
AND date_from < ADD_MONTHS( :start_date, :number_months )
GROUP BY id_othertable
UNION ALL
SELECT id_othertable,
date_to,
LEAD( date_from, 1, ADD_MONTHS( :start_date, :number_months ) )
OVER ( PARTITION BY id_othertable ORDER BY date_from )
FROM some_dates
WHERE date_to > :start_date
AND date_from < ADD_MONTHS( :start_date, :number_months )
)
SELECT id,
date_from,
date_to
FROM dates
WHERE date_from < date_to
ORDER BY id, date_from;