I am trying to merge rows with overlapping date intervals in a table in Impala SQL. However the solutions I have found to solve this are not supported by Impala eg. WHERE EXISTS and recursive CTEs.
How would I write a query for this in Impala?
Table: @T
ID StartDate EndDate
1 20170101 20170201
2 20170101 20170401
3 20170505 20170531
4 20170530 20170531
5 20170530 20170831
6 20171001 20171005
7 20171101 20171225
8 20171105 20171110
Required Output:
StartDate EndDate
20170101 20170401
20170505 20170831
20171001 20171005
Example of what I am trying to achieve that is not supported in Impala:
SELECT
s1.StartDate,
MIN(t1.EndDate) AS EndDate
FROM @T s1
INNER JOIN @T t1 ON s1.StartDate <= t1.EndDate
AND NOT EXISTS(SELECT * FROM @T t2
WHERE t1.EndDate >= t2.StartDate AND t1.EndDate < t2.EndDate)
WHERE NOT EXISTS(SELECT * FROM @T s2
WHERE s1.StartDate > s2.StartDate AND s1.StartDate <= s2.EndDate)
GROUP BY s1.StartDate
ORDER BY s1.StartDate
Similar questions:
Merge overlapping date intervals
Eliminate and reduce overlapping date ranges
https://gerireshef.wordpress.com/2010/05/02/packing-date-intervals/
https://www.sqlservercentral.com/Forums/Topic826031-8-1.aspx
select min(StartDate) as StartDate
,max(EndDate) as EndDate
from (select StartDate,EndDate
,count (is_gap) over
(
order by StartDate,ID
) as range_id
from (select ID,StartDate,EndDate
,case
when max (EndDate) over
(
order by StartDate,ID
rows between unbounded preceding
and 1 preceding
) < StartDate
then true
end as is_gap
from t
) t
) t
group by range_id
order by StartDate
;
+------------+------------+
| startdate | enddate |
+------------+------------+
| 2017-01-01 | 2017-04-01 |
| 2017-05-05 | 2017-08-31 |
| 2017-10-01 | 2017-10-05 |
| 2017-11-01 | 2017-12-25 |
+------------+------------+
来源：https://stackoverflow.com/questions/43591804/impala-sql-merging-rows-with-overlapping-dates-where-exists-and-recursive-cte