Time addition based on previous column partition by different object

Question

I asked a question on Time addition based on the previous row.

Now I have another one related to that question. Appreciate if someone could give me some help. I use the following code to create the data my need.

create temporary table test(object varchar(10),
                            id integer,
                            realtime datetime,
                            realminute float(15));

insert into test(object, id, realtime, realminute) values
("A","1","2018-12-12 03:03:03","96"),
("B","1","2018-12-12 05:24:01","15");

insert into test(object, id, realminute) values
("A","2","15"),
("A","3","10"),
("A","4","30"),
("A","5","30"),
("A","6","15"),
("B","2","15"),
("B","3","15"),
("B","4","15"),
("B","5","15"),
("B","6","15");

Then I have this.

object|id|          realtime                      | realminute
     A|1|           2018-12-12 03:03:03           |  96
     A|2|                                         |  15
     A|3|                                         |  10
     A|4|                                         |  30
     A|5|                                         |  30
     A|6|                                         |  15
     B|1|           2018-12-12 05:24:01           |  15
     B|2|                                         |  15
     B|3|                                         |  15
     B|4|                                         |  15
     B|5|                                         |  15
     B|6|                                         |  15

For object A, 2018-12-12 03:03:03 plus 96 minutes would be 2018-12-12 04:39:03. This is the realtime for object A in the second column. For object B, 2018-12-12 05:24:01 plus 15 minutes would be 2018-12-12 05:39:01. This is the realtime for object B in the second column. The following table is what I need.

object|id|          realtime  | realminute
     A|1| 2018-12-12 03:03:03 |  96
     A|2| 2018-12-12 04:39:03 |  15
     A|3| 2018-12-12 04:54:03 |  10
     A|4| 2018-12-12 05:04:03 |  30
     A|5| 2018-12-12 05:34:03 |  30
     A|6| 2018-12-12 06:04:03 |  15
     B|1| 2018-12-12 05:24:01 |  15
     B|2| 2018-12-12 05:39:01 |  15
     B|3| 2018-12-12 05:54:01 |  15
     B|4| 2018-12-12 06:09:01 |  15
     B|5| 2018-12-12 06:24:01 |  15
     B|6| 2018-12-12 06:39:01 |  15

How could I get this result?

Answer 1

SELECT CASE WHEN realtime IS NULL AND @object = object 
            THEN @realtime 
            ELSE @realtime := realtime 
            END realtime,
       realminute,
       @object := object object,
       id,
       @realtime := @realtime + INTERVAL realminute MINUTE nextrealtime
FROM test, (SELECT @object:='',@realtime:='') vars
ORDER BY object, id;

-

| realtime            | object | nextrealtime        | realminute | id  |
| ------------------- | ------ | ------------------- | ---------- | --- |
| 2018-12-12 03:03:03 | A      | 2018-12-12 04:39:03 | 96         | 1   |
| 2018-12-12 04:39:03 | A      | 2018-12-12 04:54:03 | 15         | 2   |
| 2018-12-12 04:54:03 | A      | 2018-12-12 05:04:03 | 10         | 3   |
| 2018-12-12 05:04:03 | A      | 2018-12-12 05:34:03 | 30         | 4   |
| 2018-12-12 05:34:03 | A      | 2018-12-12 06:04:03 | 30         | 5   |
| 2018-12-12 06:04:03 | A      | 2018-12-12 06:19:03 | 15         | 6   |
| 2018-12-12 05:24:01 | B      | 2018-12-12 05:39:01 | 15         | 1   |
| 2018-12-12 05:39:01 | B      | 2018-12-12 05:54:01 | 15         | 2   |
| 2018-12-12 05:54:01 | B      | 2018-12-12 06:09:01 | 15         | 3   |
| 2018-12-12 06:09:01 | B      | 2018-12-12 06:24:01 | 15         | 4   |
| 2018-12-12 06:24:01 | B      | 2018-12-12 06:39:01 | 15         | 5   |
| 2018-12-12 06:39:01 | B      | 2018-12-12 06:54:01 | 15         | 6   |

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