问在case when语句-Snowflake中，无法基于不同的列串接值

EN

with data as (
    select null checkouttime
        , 2 primarypatientinsuranceid
        , null closedby
        , 4 billingtabcheckeddate
        , 5 alreadyrouted
)

select array_to_string(array_construct_compact(
    iff(checkouttime is null, 'Patient is not checked out', null) 
    , iff(primarypatientinsuranceid is null, 'No insurance information', null)
    , iff(closedby is null, 'Encounter not signed off', null)
    , iff(billingtabcheckeddate is null, 'Billing tab is not checked', null)
    , iff(alreadyrouted is null, 'Missing slip already routed', 'Valid Missing slip')
    ), ',  ')
as resultant
from data

select 
case when true then ',Patient is not checked out' else '' END
|| case when false then ',No insurance information' else '' END
|| case when true then ',Encounter not signed off' else '' END
|| case when true then ',Billing tab is not checked' else '' END
|| case when false then ',Missing slip already routed' else 'Valid Missing slip' END 
as resultant;