how to convert jsonarray to multi column from hive - sql

Question

example:
there is a json array column(type:string) from a hive table like:
"[{"filed":"name", "value":"alice"}, {"filed":"age", "value":"14"}......]"
how to convert it into :
name age
alice 14
by hive sql?
I've tried lateral view explode but it's not working.
thanks a lot!

Answer 1

This is working example of how it can be parsed in Hive. Customize it yourself and debug on real data, see comments in the code:
with your_table as (
select stack(1,
1,
'[{"field":"name", "value":"alice"}, {"field":"age", "value":"14"}, {"field":"something_else", "value":"somevalue"}]'
) as (id,str) --one row table with id and string with json. Use your table instead of this example
)
select id,
max(case when field_map['field'] = 'name' then field_map['value'] end) as name,
max(case when field_map['field'] = 'age' then field_map['value'] end) as age --do the same for all fields
from
(
select t.id,
t.str as original_string,
str_to_map(regexp_replace(regexp_replace(trim(a.field),', +',','),'\\{|\\}|"','')) field_map --remove extra characters and convert to map
from your_table t
lateral view outer explode(split(regexp_replace(regexp_replace(str,'\\[|\\]',''),'\\},','}|'),'\\|')) a as field --remove [], replace "}," with '}|" and explode
) s
group by id --aggregate in single row
;
Result:
OK
id name age
1 alice 14
One more approach using get_json_object:
with your_table as (
select stack(1,
1,
'[{"field":"name", "value":"alice"}, {"field":"age", "value":"14"}, {"field":"something_else", "value":"somevalue"}]'
) as (id,str) --one row table with id and string with json. Use your table instead of this example
)
select id,
max(case when field = 'name' then value end) as name,
max(case when field = 'age' then value end) as age --do the same for all fields
from
(
select t.id,
get_json_object(trim(a.field),'$.field') field,
get_json_object(trim(a.field),'$.value') value
from your_table t
lateral view outer explode(split(regexp_replace(regexp_replace(str,'\\[|\\]',''),'\\},','}|'),'\\|')) a as field --remove [], replace "}," with '}|" and explode
) s
group by id --aggregate in single row
;
Result:
OK
id name age
1 alice 14