Extract the highest key:value pair from a string in Standard SQL
Consider below approach
select column,
( select cast(split(kv, '=')[offset(0)] as int64)
from unnest(regexp_extract_all(column, r'(\d+=\d+.\d+)')) kv
order by cast(split(kv, '=')[offset(1)] as float64) desc
limit 1
) key
from your_table
if applied to sample data in your question - output is
