I have been struggling to merge datetime ranges in oracle SQL/PLSQL (Database Standard Edition 11gR2).

I am trying to merge datetime ranges so that the following data

```
order_id    start_date_time         end_date_time
3933        04/02/2020 08:00:00     04/02/2020 12:00:00
3933        04/02/2020 13:30:00     04/02/2020 17:00:00
3933        04/02/2020 14:00:00     04/02/2020 19:00:00
3933        05/02/2020 13:40:12     05/02/2020 14:34:48
3933        05/02/2020 14:00:00     05/02/2020 18:55:12
3933        05/02/2020 14:49:48     05/02/2020 15:04:48
3933        06/02/2020 08:00:00     06/02/2020 12:00:00
3933        06/02/2020 13:30:00     06/02/2020 17:00:00
3933        06/02/2020 14:10:12     06/02/2020 18:49:48
3933        07/02/2020 08:00:00     07/02/2020 10:30:00
3933        07/02/2020 08:00:00     07/02/2020 12:00:00
3933        07/02/2020 13:30:00     07/02/2020 17:00:00
11919       14/05/2020 09:00:00     14/05/2020 17:00:00
11919       14/05/2020 09:00:00     14/05/2020 17:00:00
11919       14/05/2020 15:00:00     14/05/2020 16:30:00
11919       15/05/2020 08:40:12     15/05/2020 16:30:00
11919       15/05/2020 09:40:12     15/05/2020 16:30:00
11919       15/05/2020 10:15:00     15/05/2020 12:15:00
11919       15/05/2020 13:19:48     15/05/2020 16:00:00
11919       18/05/2020 08:49:48     18/05/2020 09:45:00
11919       18/05/2020 10:00:00     18/05/2020 17:00:00
11919       18/05/2020 10:00:00     18/05/2020 16:58:12
11919       18/05/2020 15:34:48     18/05/2020 16:10:12
11919       18/05/2020 16:30:00     18/05/2020 16:45:00
...         ...                     ...

```

would transform into the following result set

```
--after merge (this is the result I am seeking)
order_id    start_date_time         end_date_time
3933        04/02/2020 08:00:00     04/02/2020 12:00:00
3933        04/02/2020 13:30:00     04/02/2020 19:00:00
3933        05/02/2020 13:40:12     05/02/2020 18:55:12
3933        06/02/2020 08:00:00     06/02/2020 12:00:00
3933        06/02/2020 13:30:00     06/02/2020 18:49:48
3933        07/02/2020 08:00:00     07/02/2020 12:00:00
3933        07/02/2020 13:30:00     07/02/2020 17:00:00
11919       14/05/2020 09:00:00     14/05/2020 17:00:00
11919       15/05/2020 08:40:12     15/05/2020 16:30:00
11919       18/05/2020 08:49:48     18/05/2020 17:00:00
...         ...                     ...

```

The format of start\_date\_time and end\_date\_time is DAY/MONTH/YEAR HH24:MI:SS.

Any suggestion/solution on how to make that merge in Oracle SQL or PL/SQL? 

I thought that was a trivial problem, however I was not able to find a solution on the internet yet.

Thanks in advance.