How to find the time gap(in minutes) between two records(two different columns) in an Oracle database

Question

I want to find the time gaps for different days between one end_time and nearest start_time in another record which is stored as follows:

record_id | start_time | end_time
120 | 2019-09-01 08:05:00 | 2019-09-01 10:35:00 
103 | 2019-09-01 10:45:00 | 2019-09-01 14:00:00
108 | 2019-09-01 14:30:00 | 2019-09-01 18:00:00
225 | 2019-09-02 07:30:00 | 2019-09-02 10:30:00
245 | 2019-09-02 10:30:00 | 2019-09-02 13:40:00 
250 | 2019-09-02 14:00:00 | null

Start_time and End_time are timestamp columns.

Expected output is:

2019-09-01 | 10
2019-09-01 | 30
2019-09-02 |  0
2019-09-02 | 20

Can anyone please help me on this?

Answer 1

Here you will need to use LEAD analytic function.

select end_time, 
       lead(start_time) over (order by start_time) as nextr -- this is the start_time from the next record
from   your_table;

Then you can select (next_record - start_time) to get the tipe gap and format it in away you want.

Hope this will help you. Here is the example of what you need: http://sqlfiddle.com/#!4/23457/3

First I have created the example table:

create table your_table (
record_id number(10),
start_time date,
end_time date);

insert into your_table values (101, to_date('02.10.2019 08:00:00','dd.mm.yyyy hh24:mi:ss'), to_date('02.10.2019 12:00:00','dd.mm.yyyy hh24:mi:ss'));
insert into your_table values (102, to_date('02.10.2019 12:30:00','dd.mm.yyyy hh24:mi:ss'), to_date('03.10.2019 12:00:00','dd.mm.yyyy hh24:mi:ss'));
insert into your_table values (103, to_date('03.10.2019 12:10:00','dd.mm.yyyy hh24:mi:ss'), to_date('03.10.2019 15:00:00','dd.mm.yyyy hh24:mi:ss'));
insert into your_table values (104, to_date('03.10.2019 15:15:00','dd.mm.yyyy hh24:mi:ss'), to_date('03.10.2019 18:00:00','dd.mm.yyyy hh24:mi:ss'));

And on the right you have the code that will return the result you asked for:

select start_time, 
       --lead(start_time) over (order by start_time) as nextr,
       (nvl(((lead(start_time) over (order by start_time)) - end_time), 0)) * 24 * 60 AS "Time gap"
from   your_table;