What is the best way to work around data? - oracle

Question

I am trying to display data as such:
In our database we have events (with unique ID) and then a start date. The events do not overlap, and each one starts on the date the last one ended. However we don't have 'end date' in the database.
I have to feed the data into another system so that it shows event ID, start date, and end date (which is just the next start date).
I want to avoid creating a custom view as that's really frowned upon here for this database. So I'm wondering if there's a good way to do this in a query.
Essentially it would be:
EventA | Date1 | Date2
EventB | Date2 | Date3
EventC | Date3 | Date4
The events are planned years in advance and I only need to have the next few months pulled for the query, so no worry about running out of 'next event start dates' and in case it matters, this query will be part of a webservice call.
The basic pseudo code for event and date would be:
select Event.ID, Event.StartDate
from Event
where Event.StartDate > sysdate and Event.StartDate < sysdate+90
Essentially I want to take the next row's Event.StartDate and make it the current row's Event.EndDate

Answer 1

Use the LEAD analytic function:
Oracle Setup:
A table with 10 rows:
CREATE TABLE Event ( ID, StartDate ) AS
SELECT LEVEL, TRUNC( SYSDATE ) + LEVEL
FROM DUAL
CONNECT BY LEVEL <= 10;
Query:
select ID,
StartDate,
LEAD( StartDate ) OVER ( ORDER BY StartDate ) AS EndDate
from Event
where StartDate > sysdate and StartDate < sysdate+90
Output:
ID | STARTDATE | ENDDATE
-: | :-------- | :--------
1 | 22-JUN-19 | 23-JUN-19
2 | 23-JUN-19 | 24-JUN-19
3 | 24-JUN-19 | 25-JUN-19
4 | 25-JUN-19 | 26-JUN-19
5 | 26-JUN-19 | 27-JUN-19
6 | 27-JUN-19 | 28-JUN-19
7 | 28-JUN-19 | 29-JUN-19
8 | 29-JUN-19 | 30-JUN-19
9 | 30-JUN-19 | 01-JUL-19
10 | 01-JUL-19 | null
db<>fiddle here