Duration of each status PostgreSQL - postgresql

Question

I have a table that has a couple of statuses for each ticket - e.g:
OPENED
CLOSED
RE-OPENED
FINISHED
REJECTED
...
And each row in the status table has the timestamp of when a status was set / changed, something like this:
time
status
2021-11-22 09:40
OPENED
2021-11-22 09:50
CLOSED
2021-11-22 10:10
RE-OPENED
2021-11-22 10:30
FINISHED
2021-11-22 10:50
CLOSED
2021-11-22 11:30
RE-OPENED
2021-11-22 12:10
REJECTED
What I am interested in, is how to calculate the duration of each status in a time range?
Time range can be anything from one hour to a couple of days. Let's use an example and try to calculate the duration for each status between
2021-11-22 10:00 - 2021-11-22 11:00
If we take a look into the table:
time
status
2021-11-22 09:50
CLOSED
2021-11-22 10:10
RE-OPENED
2021-11-22 10:30
FINISHED
2021-11-22 10:50
CLOSED
2021-11-22 11:30
RE-OPENED
10:00 - 10:10 --> CLOSED
10:10 - 10:30 --> RE-OPENED
10:30 - 10:50 --> FINISHED
10:50 - 11:00 --> CLOSED
The result table would look something like this:
status
duration
OPENED
00:00
CLOSED
00:20
RE-OPENED
00:20
REJECTED
00:00
FINISHED
00:20
P.S. As you can see, even though the first appearance of a status entry in the time range (10:00 - 11:00) was at 10:10, we have to include last reported status before the selected/desired time-range.
I appreciate the help.

Answer 1

You can use LEAD() to calculate time difference for rows which meet the time range condition. Then sum the time difference as duration. This is helpful when your time range spans a couple of hours or days.
WITH calc_table AS (
SELECT *, LEAD(CASE WHEN t1.time between
'2021-11-22 10:00' AND '2021-11-22 11:00'
THEN t1.time END) OVER (Order by t1.time) - t1.time as timediff
FROM mytable t1
)
SELECT DISTINCT c.status,
SUM(CASE WHEN c.timediff IS NOT NULL THEN c.timediff ELSE '00:00:00' END) AS duration
FROM calc_table c
GROUP BY c.status;
See the Demo