Snowflake : array_agg inside an array_agg - snowflake-cloud-data-platform

Question

I would like to perform this transformation :
below is the input and the output is the json with the "d": [ "c_value_1", "c_value_2"].
As you can see, I am working with an array of nested objects, and I would like to flatten c.
I know this involves two array_aggs, but I always end up with this error :
SQL compilation error: Unsupported subquery type cannot be evaluated
with table_1 as (
select parse_json(
'[
{
"a": "a_value_1",
"b": [
{
"c": "c_value_1",
},
{
"c": "c_value_2",
}
]
},
{
"a": "a_value_2",
"b": [
{
"c": "c_value_2",
},
{
"c": "c_value3",
}
]
}
]'
) as json_object
)
select parse_json(
'[
{
"a": "a_value_1",
"d": [ "c_value_1", "c_value_2"]
},
{
"a": "a_value_2",
"d": [ "c_value_2", "c_value_3"]
}
]'
);
The goal is to have a table with the second array of objects as a column

Answer 1

Get Path (explains how the ':' work)
Object Agg()
Object Keys (never leave home without em)
with table_1 as (
select
parse_json(
'[
{
"a": "a_value_1",
"b": [
{
"c": "c_value_1",
},
{
"c": "c_value_2",
}
]
},
{
"a": "a_value_2",
"b": [
{
"c": "c_value_2",
},
{
"c": "c_value3",
}
]
}
]'
) as json_object
)
SELECT
DISTINCT OBJECT_AGG(
h.value::string, iff(
h.value = 'a',
object_construct(h.value::string,g.value:a) ,object_construct(h.value::string,array_construct(g.value:b[0].c,g.value:b[1].c
) ) ) ) over (partition by h.seq) bob
FROM
table_1,
lateral flatten(input => json_object) g,
lateral flatten(input => object_keys(g.value)) h;
Summary.
Rip it down to the atomic(lowest) layer using the flattens ect
Build it up using the Semi Structured functions
Possible improvements - removing the IFF in the middle - just ran out of time... sorry.