Fetch latest start date, if there are two minimum start dates in a table - sql

Question

I'm trying to build a query for the following scenario,
Group records by license ID and get min and max dates
For a given license ID, if there are two earliest start dates, then start date of the particular ID has to be updated as latest start date in that grouping.
Since I'm new to sql, I need help to satisfy condition 2. Any help is greatly appreciated. Thanks
Actual data
LicenseID
StartDate
EndDate
100
4/3/2000
3/1/2013
100
4/3/2000
2/2/2017
100
3/1/2013
1/23/2015
100
1/23/2015
2/2/2017
100
2/2/2017
2/9/2018
100
2/2/2017
12/18/2018
100
12/18/2018
2/16/2021
Expected output
LicenseID
StartDate
EndDate
100
12/18/2018
2/16/2021

Answer 1

Here's one option; read comments within code.
Sample data:
SQL> with test (id, start_date, end_date) as
2 (select 100, date '2000-04-03', date '2013-03-01' from dual union all
3 select 100, date '2000-04-03', date '2017-02-02' from dual union all
4 select 100, date '2018-12-18', date '2021-02-16' from dual
5 ),
Query begins here:
6 -- rank start dates per each ID
7 temp as
8 (select id,
9 min(start_date) over (partition by id) min_sd,
10 max(start_date) over (partition by id) max_sd,
11 rank() over (partition by id order by start_date) rnk_sd,
12 --
13 max(end_date) over (partition by id) max_ed
14 from test
15 ),
16 -- count number of the 1st start dates
17 temp2 as
18 (select id,
19 sum(case when rnk_sd = 1 then 1 else 0 end) cnt_sd
20 from temp
21 group by id
22 )
23 -- if number of the 1st start dates is 1, take MIN_SD. Otherwise, take MAX_SD
24 select distinct
25 b.id,
26 case when b.cnt_sd = 1 then a.min_sd else a.max_sd end start_date,
27 a.max_ed end_date
28 from temp2 b join temp a on a.id = b.id;
Result:
ID START_DATE END_DATE
---------- ---------- ----------
100 12/18/2018 02/16/2021
SQL>

Answer 2

This can filter them:
WITH sample_data AS
(
SELECT 100 AS LicenseID, TO_DATE('04/03/2000','MM/DD/YYYY') AS StartDate, TO_DATE('03/01/2013','MM/DD/YYYY') AS EndDate FROM DUAL UNION ALL
SELECT 100, TO_DATE('04/03/2000','MM/DD/YYYY'), TO_DATE('02/02/2017','MM/DD/YYYY') FROM DUAL UNION ALL
SELECT 100, TO_DATE('03/01/2013','MM/DD/YYYY'), TO_DATE('01/23/2015','MM/DD/YYYY') FROM DUAL UNION ALL
SELECT 100, TO_DATE('01/23/2015','MM/DD/YYYY'), TO_DATE('02/02/2017','MM/DD/YYYY') FROM DUAL UNION ALL
SELECT 100, TO_DATE('02/02/2017','MM/DD/YYYY'), TO_DATE('02/09/2018','MM/DD/YYYY') FROM DUAL UNION ALL
SELECT 100, TO_DATE('02/02/2017','MM/DD/YYYY'), TO_DATE('12/18/2018','MM/DD/YYYY') FROM DUAL UNION ALL
SELECT 100, TO_DATE('12/18/2018','MM/DD/YYYY'), TO_DATE('02/16/2021','MM/DD/YYYY') FROM DUAL
)
SELECT dat.licenseID, CASE WHEN dups.licenseID IS NOT NULL THEN MAX(StartDate)
ELSE MIN(StartDate)
END,
CASE WHEN dups.licenseID IS NOT NULL THEN MAX(EndDate)
ELSE MIN(EndDate)
END
FROM sample_data dat
LEFT OUTER JOIN (SELECT COUNT(1), sd.LicenseID
FROM sample_data sd
INNER JOIN (SELECT MIN(StartDate) AS StartDate, LicenseID
FROM sample_data
GROUP BY LicenseID) mins
ON sd.LicenseID = mins.LicenseID AND sd.startDate = mins.StartDate
GROUP BY sd.LicenseID
HAVING COUNT(1) > 1) dups
ON dups.LicenseID = dat.licenseID
GROUP BY dat.licenseID, dups.licenseID;

Answer 3

You can use:
SELECT licenseid,
MAX(startdate) AS startdate,
MAX(enddate) KEEP (DENSE_RANK LAST ORDER BY startdate) AS enddate
FROM table_name
GROUP BY licenseid
HAVING COUNT(*) KEEP (DENSE_RANK FIRST ORDER BY startdate) > 1;
or:
SELECT licenseid,
max_startdate AS startdate,
max_enddate As enddate
FROM (
SELECT licenseid,
RANK()
OVER (PARTITION BY licenseid ORDER BY startdate) AS rnk,
ROW_NUMBER()
OVER (PARTITION BY licenseid, startdate ORDER BY enddate) AS rn,
MAX(startdate)
OVER (PARTITION BY licenseid) AS max_startdate,
MAX(enddate)
KEEP (DENSE_RANK LAST ORDER BY startdate)
OVER (PARTITION BY licenseid) AS max_enddate
FROM table_name t
)
WHERE rnk = 1
AND rn = 2;
Which, for the sample data:
CREATE TABLE table_name (licenseid, startdate, enddate) AS
SELECT 100, DATE'2000-04-03', DATE'2013-03-01' FROM DUAL UNION ALL
SELECT 100, DATE'2000-04-03', DATE'2017-02-02' FROM DUAL UNION ALL
SELECT 100, DATE'2013-03-01', DATE'2015-01-23' FROM DUAL UNION ALL
SELECT 100, DATE'2015-01-23', DATE'2017-02-02' FROM DUAL UNION ALL
SELECT 100, DATE'2017-02-02', DATE'2018-02-09' FROM DUAL UNION ALL
SELECT 100, DATE'2018-02-02', DATE'2018-12-18' FROM DUAL UNION ALL
SELECT 100, DATE'2018-12-18', DATE'2021-02-16' FROM DUAL;
Both output:
LICENSEID
STARTDATE
ENDDATE
100
2018-12-18 00:00:00
2021-02-16 00:00:00
If you do want to perform an UPDATE of that second row then:
MERGE INTO table_name dst
USING (
SELECT ROWID AS rid,
max_startdate,
max_enddate
FROM (
SELECT RANK()
OVER (PARTITION BY licenseid ORDER BY startdate) AS rnk,
ROW_NUMBER()
OVER (PARTITION BY licenseid, startdate ORDER BY enddate) AS rn,
MAX(startdate)
OVER (PARTITION BY licenseid) AS max_startdate,
MAX(enddate)
KEEP (DENSE_RANK LAST ORDER BY startdate)
OVER (PARTITION BY licenseid) AS max_enddate
FROM table_name t
)
WHERE rnk = 1
AND rn = 2
)src
ON (src.rid = dst.ROWID)
WHEN MATCHED THEN
UPDATE
SET startdate = src.max_startdate,
enddate = src.max_enddate;
db<>fiddle here