Finding gaps between date ranges spanning records - sql

Question

I'm trying to write a query where I can find any gap in the date ranges for a given ID when passing in two dates.
EDIT: I need to know if a whole gap or part of a gap exists in my date range.
I have data in this format:
Example 1:
| ID | START_DATE | END_DATE |
|----|------------|------------|
| 1 | 01/01/2019 | 30/09/2019 |
| 1 | 01/03/2020 | (null) |
Example 2:
| ID | START_DATE | END_DATE |
|----|------------|------------|
| 2 | 01/01/2019 | 30/09/2019 |
| 2 | 01/10/2019 | 01/12/2019 |
| 2 | 02/12/2019 | (null) |
NB. A null end date essentially means "still active up to current day".
E.g. Example 1 has a gap of 152 days between 30/09/2019 and 01/03/2020. If I queried in the range of 05/05/2019 - 01/09/2019 there's no gap in that range. Whereas if I'm looking at the date range 05/05/2019 - 02/10/2019 there's a single day gap in that range.
For what it's worth, I don't actually care how many days gap, just whether there is one or not.
I've tried doing something like this but it doesn't work when my date falls into a gap:
SELECT SUM(START_DATE - PREV_END - 1)
FROM
(
SELECT ID, START_DATE, END_DATE, LAG(END_DATE) OVER (ORDER BY START_DATE) AS PREV_END_DATE
FROM TBL
WHERE ID = X_ID
)
WHERE START_DATE >= Y_FIRST_DATE
AND START_DATE <= Z_SECOND_DATE;
X_ID, Y_FIRST_DATE, and Z_SECOND_DATE are just any different ID or date range I might want to pass in.
How could I go about this?

Answer 1

Another option to determine the days might be by use SELECT .. FROM dual CONNECT BY LEVEL <= syntax through EXISTence of gaps by INTERSECTing two sets, one finds all dates between extremum parameters while the other finds all the dates fitting within the dates inserted into table as bounds :
SELECT CASE WHEN
SUM( 1 + LEAST(Z_SECOND_DATE,NVL(END_DATE,TRUNC(SYSDATE)))
- GREATEST(Y_FIRST_DATE,START_DATE) ) = Z_SECOND_DATE - Y_FIRST_DATE + 1 THEN
'NO Gap'
ELSE
'Gap Exists'
END "gap?"
FROM TBL t
WHERE ID = X_ID
AND EXISTS ( SELECT Y_FIRST_DATE + LEVEL - 1
FROM dual
CONNECT BY LEVEL <= Z_SECOND_DATE - Y_FIRST_DATE + 1
INTERSECT
SELECT t.START_DATE + LEVEL - 1
FROM dual
CONNECT BY LEVEL <= NVL(t.END_DATE,TRUNC(SYSDATE))- t.START_DATE + 1
)
START_DATE values are assumed to be non-null based on the sample data.
Demo

Answer 2

This is another variation the islands-and-gaps problem that pops up a lot here. I think this fits with Oracle's pattern matching functionality. Take this example:
WITH tbl AS
(
SELECT 1 AS ID, to_date('01/01/2019', 'DD/MM/YYYY') AS START_DATE, to_date('30/09/2019', 'DD/MM/YYYY') AS END_DATE FROM DUAL
UNION ALL
SELECT 1 AS ID, to_date('01/03/2020', 'DD/MM/YYYY') AS START_DATE, NULL AS END_DATE FROM DUAL
UNION ALL
SELECT 2 AS ID, to_date('01/01/2019', 'DD/MM/YYYY') AS START_DATE, to_date('30/09/2019', 'DD/MM/YYYY') AS END_DATE FROM DUAL
UNION ALL
SELECT 2 AS ID, to_date('01/10/2019', 'DD/MM/YYYY') AS START_DATE, to_date('01/12/2019', 'DD/MM/YYYY') AS END_DATE FROM DUAL
UNION ALL
SELECT 2 AS ID, to_date('02/12/2019', 'DD/MM/YYYY') AS START_DATE, NULL AS END_DATE FROM DUAL
)
SELECT *
FROM tbl
MATCH_RECOGNIZE(ORDER BY ID, start_date
MEASURES b.id AS ID,
a.end_date+1 AS GAP_START,
b.start_date-1 AS GAP_END
PATTERN (A B+)
DEFINE B AS start_date > PREV(end_date)+1 AND ID = PREV(ID))L;
I know it looks long, but most of it is creating the WITH clause. The pattern matching allows you to define what a gap is and pull the information accordingly. Notice that in order to have a gap, your start date must be greater than the previous end date + 1 grouped by the ID column.
To enhance this to answer your updated/edited question, just add this line of code to the end:
WHERE GREATEST(gap_start, TO_DATE('15/09/2019', 'DD/MM/YYYY' /*Y_FIRST_DATE*/)) <= LEAST(gap_end, to_date('15/10/2019', 'DD/MM/YYYY')/*Z_SECOND_DATE*/)

Answer 3

You can split the date range you are passing, into dates and then compare it with a date range in your table as follows:
SELECT
CASE WHEN SUM(CASE WHEN T.ID IS NULL THEN 1 END) > 0
THEN 'THERE IS GAP'
ELSE 'THERE IS NO GAP'
END AS RESULT_
FROM ( SELECT P_IN_FROM_DATE + LEVEL - 1 AS CUST_DATES
FROM DUAL
CONNECT BY LEVEL <= P_IN_TO_DATE - P_IN_FROM_DATE + 1
) CUST_TBL
LEFT JOIN TBL T
ON CUST_TBL.CUST_DATES BETWEEN T.START_DATE AND T.END_DATE
OR ( CUST_TBL.CUST_DATES >= T.START_DATE AND T.END_DATE IS NULL )

Answer 4

I would suggest finding the maximum end date before the current record -- based on the start date.
That would be:
select t.*
from (select t.*,
max(end_date) over (order by start_date
rows between unbounded preceding and 1 preceding
) as max_prev_end_date
from tbl t
where start_date <= :input_end_date and
end_date >= :input_start_date
) t
where max_prev_end_date < start_date;