UPDATE statement GA4 Big Query SQL with events and UNNEST - google-bigquery

Question

I'm trying to find a way to update records that have a event_name page_view and key page_location where the latter is containing some pattern. The query below gives me the selection I'm after. Now the problem is that I cannot wrap my head around how to include and UPDATE statement to change the values of page_location in that selection. Do you know?
SELECT *
FROM (
SELECT (SELECT value.string_value FROM UNNEST(event_params) WHERE event_name = 'page_view' AND key = 'page_location') AS page
FROM `project-name.analytics_299XXXXXX.events_*`
WHERE
_table_suffix BETWEEN '20220322'
AND FORMAT_DATE('%Y%m%d',DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY)) AND
event_name = 'page_view'
LIMIT 1000
) x
WHERE x.page LIKE '%login%';

Answer 1

If I understand you correctly i think you should use the following pattern. Google docs don't have this update pattern listed which is a shame as it's the most useful IMO:
update ds.targettable t
set t.targetfield = s.sourcefield
from (select keyfield, sourcefield
from ds.sourcetable
) s
where t.keyfield = s.keyfield
I apologize in advance as I don't have access to the GA events table so i've just coded this up from the top of my head; here is some code that should get you close:
update `project-name.analytics_299XXXXXX.events_*` tgt
set page_location = src.page
from (SELECT event_name, key, _table_suffix (SELECT value.string_value FROM UNNEST(event_params) WHERE event_name = 'page_view' AND key = 'page_location') AS page
FROM `project-name.analytics_299XXXXXX.events_*`
WHERE _table_suffix BETWEEN '20220322'
AND FORMAT_DATE('%Y%m%d',DATE_SUB(CURRENT_DATE(), INTERVAL 1 DAY))
AND event_name = 'page_view'
and page LIKE '%login%') src
--join tables together on PK (or make one)
where farm_fingerprint(concat(tgt.key, tgt.event_name) = farm_fingerprint(concat(src.key, src.event_name)
and src._table_suffix = tgt._table_suffix
and tgt.page LIKE '%login%'
I'm not exactly sure how to manage the table suffix so you may need to play with that