Count unique within combination of json keys in BigQuery - sql

Question

In BigQuery I do have a json stored in 1 column like this:
{"key1": "value1", "key3":"value3"}
{"key2": "value2"}
{"key3": "value3"}
What I'd want to know is how to calculate number of unique combinations, paying attention that there can be up to 100+ different keys so avoiding listing them would be beneficial.
In example above end result of unique number will be 2, because first and third matched by "key3", while second didn't matched with anything.
I understand how to build this with writing an app that will calculate it, but would like to see if there is any solution possible with 1 query

Answer 1

If your JSON values are formatted with no spaces after the :, then you can treat this as string manipulations:
with t as (
select '{"key1":"value1", "key3":"value3"}' as kv union all
select '{"key2":"value2"}' union all
select '{"key3":"value3"}'
)
select x, count(*)
from t cross join
unnest(regexp_extract_all(t.kv, '"[^,]+"')) x
group by x
having count(*) = 1;
With the spaces, you can use replace() to get rid of them:
with t as (
select '{"key1": "value1", "key3":"value3"}' as kv union all
select '{"key2": "value2"}' union all
select '{"key3": "value3"}'
)
select replace(x, '": "', '":"'), count(*)
from t cross join
unnest(regexp_extract_all(t.kv, '"[^,]+"')) x
group by 1
having count(*) = 1;