Transform your long data to wide data - to break down the request in phases

wide_to_long.sql

create or replace table `PROJECTNAME.DATASETNAME.performance_long` partition by DATE(timestamp) as 

with base as (
	select
		timestamp, date, event_timestamp, clientid, user_id, device_category, country, url, hostname,
		page_path, page_title, page_referrer, type
	from `PROJECTNAME.DATASETNAME.performance_wide`
)

,intervals as (
	select event_timestamp, clientid,
		'Prompt for unload' as phase, unloadeventend - unloadeventstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'Redirect' as phase, redirectend - redirectstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'AppCache' as phase, domainlookupstart - fetchstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'DNS' as phase, connectstart - domainlookupstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'TCP' as phase, requeststart - connectstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'Request' as phase, responsestart - requeststart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'Response' as phase, responseEnd - responsestart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'To domInteractive' as phase, dominteractive - responseEnd as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'domInteractive to Complete' as phase, domcomplete - dominteractive as value
	from `PROJECTNAME.DATASETNAME.performance_wide`
	union all
	select event_timestamp, clientid,
		'Load' as phase, loadeventend - loadeventstart as value
	from `PROJECTNAME.DATASETNAME.performance_wide`

)

select * from base right join intervals using(event_timestamp, clientid)

See this guide on how to measure web performance data in bigquery for context

See the source data query for this query here