Snowflake SQL: trying to calculate time difference between subsets of subsequent rows

Question

I have some data like the following in a Snowflake database

DEVICE_SERIAL	REASON_CODE	VERSION	MESSAGE_CREATED_AT	NEXT_REASON_CODE
BA1254862158	1	4	2022-06-23 02:06:03	4
BA1254862158	4	4	2022-06-23 02:07:07	1
BA1110001111	1	5	2022-06-16 16:19:04	4
BA1110001111	4	5	2022-06-16 17:43:04	1
BA1110001111	5	5	2022-06-20 14:37:45	4
BA1110001111	4	5	2022-06-20 17:31:12	1

that's the result of a previous query. I'm trying to get the difference between message_created_at timestamps where the device_serial is the same between subsequent rows, and the first row (of the pair for the difference) has reason_code of 1 or 5 , and the second row of the pair has reason_code 4 .

For this example, my desired output would be

DEVICE_SERIAL	VERSION	DELTA_SECONDS
BA1254862158	4	64
BA1110001111	5	5040
BA1110001111	5	10407

It's easy to calculate the time difference between every pair of rows (just lead or lag + datediff). But I'm not sure how to structure a query to select only the desired rows so that I can get a datediff between them, without calculating spurious datediffs.

My ultimate goal is to see how these datediffs change between version s. I am but a lowly C programmer, my SQL-fu is weak.

Answer 1

with data as (
    select *,
        count(case when reason_code in (1, 5) then 1 end)
            over (partition by device_serial order by message_created_at) as grp
        /* or alternately bracket by the end code */
        -- count(case when reason_code = 4 then 1 end)
            -- over (partition by device_serial order by message_created_at desc) as grp

    from T
)
select device_serial, min(version) as version,
    datediff(second, min(message_created_at), max(message_created_at)) as delta_seconds
from data
group by device_serial, grp