loop in Big query

create or preplace procedure `proc_name`
BEGIN
declare k_array ARRAY<struct><banner string, intiative_type string>;
set k_array =
( 
select array_agg(meta) from
(SELECT struct(banner,initiative_type) as meta
from storing_table
) t
);

for element in (
select * from unnest(k_array)) DO
EXECUTE IMMEDIATE format(
""" SELECT '%s'  # this is arg1
""",
element.banner.element.initiative_type

)