How to group user sessions by converted row - sql

Question

I'm doing simple multichannel attribution exploration and got stuck with grouping user sessions.
For example, I have simple sessions table:
client channel time converted
1 social 1 0
1 cpc 2 0
1 email 3 1
1 email 4 0
1 cpc 5 1
2 organic 1 0
2 cpc 2 1
3 email 1 0
Each row contains user sessions and converted column, which shows if user converted in particular session.
I need to group sessions which lead conversion for each user and for each conversion, so perfect result should be:
client channels time converted
1 [social,cpc,email] 3 1
1 [email,cpc] 5 1
2 [organic,cpc] 2 1
3 [email] 1 0
Notice user 3, he's not converted but I need to have his sessions

Answer 1

You need to assign a group. For this purpose, an inverse sum of converted looks like the right thing:
select client, array_agg(channel order by time) as channels,
max(time) as time, max(converted) as converted
from (select t.*,
sum(t.converted) over (partition by t.client order by t.time desc) as grp
from t
) t
group by client, grp;

Answer 2

Below is for BigQuery Standard SQL
#standardSQL
SELECT
client,
STRING_AGG(channel ORDER BY time) channels,
MAX(time) time,
MAX(converted) converted
FROM (
SELECT *, COUNTIF(converted = 1) OVER(PARTITION BY client ORDER BY time DESC) session
FROM `project.dataset.table`
)
GROUP BY client, session
-- ORDER BY client, time
You can test, play with above using sample data from your question as in example below
#standardSQL
WITH `project.dataset.table` AS (
SELECT 1 client, 'social' channel, 1 time, 0 converted UNION ALL
SELECT 1, 'cpc', 2, 0 UNION ALL
SELECT 1, 'email', 3, 1 UNION ALL
SELECT 1, 'email', 4, 0 UNION ALL
SELECT 1, 'cpc', 5, 1 UNION ALL
SELECT 2, 'organic', 1, 0 UNION ALL
SELECT 2, 'cpc', 2, 1 UNION ALL
SELECT 3, 'email', 1, 0
)
SELECT
client,
STRING_AGG(channel ORDER BY time) channels,
MAX(time) time,
MAX(converted) converted
FROM (
SELECT *, COUNTIF(converted = 1) OVER(PARTITION BY client ORDER BY time DESC) session
FROM `project.dataset.table`
)
GROUP BY client, session
ORDER BY client, time
with result
Row client channels time converted
1 1 social,cpc,email 3 1
2 1 email,cpc 5 1
3 2 organic,cpc 2 1
4 3 email 1 0