Summarizing data using SQL - sql

Question

I have a problem that I am trying to solve using SQL and I needed your inputs on the approach to go about it.
This is how the input data & expected output looks like:
container_edits - This is the input table
container | units | status | move_time
-------------------------------------------------
XYZ | 5 | Start | 2018-01-01 00:00:15
XYZ | 2 | Add | 2018-01-01 00:01:10
XYZ | 3 | Add | 2018-01-01 00:02:00
XYZ | null | Complete | 2018-01-01 00:03:00
XYZ | 5 | Start | 2018-01-01 00:04:15
XYZ | 3 | Add | 2018-01-01 00:05:10
XYZ | 4 | Add | 2018-01-01 00:06:00
XYZ | 5 | Add | 2018-01-01 00:07:10
XYZ | 6 | Add | 2018-01-01 00:08:00
XYZ | null | Complete | 2018-01-01 00:09:00
Expected summarized output
container | loop_num | units | start_time | end_time
------------------------------------------------------------------------
XYZ | 1 | 10 | 2018-01-01 00:00:15 | 2018-01-01 00:03:00
XYZ | 2 | 23 | 2018-01-01 00:04:15 | 2018-01-01 00:09:00
Essentially, I need to partition the data based on the status label, extract the minimum and maximum time within the partition and get the total number of units within that partition. I am aware of the usage of window functions and the partition by clause but I am unclear on how to apply that when I need to partition based on the value of a column ('status' in this case).
Any leads on how to go about solving this would be really helpful. Thank you!

Answer 1

You can assign a group using a cumulative sum of starts -- which is your loop_num The rest is aggregation:
select container, loop_num, sum(units),
min(move_time), max(move_time)
from (select ce.*,
sum(case when status = 'Start' then 1 else 0 end) over (partition by container order by move_time) as loop_num
from container_edits ce
) ce
group by container, loop_num;
Here is a db<>fiddle (it happens to use Postgres, but the syntax is standard SQL).