how can I make result of ARRAY_AGG() function json parsable - sql

Question

I have a query that selects the rows from joined table as an array using ARRAY_AGG() function.
select
entity_number,
ARRAY_AGG('{"property_id":"'||property_id||'","value":"'||value||'"}') entity_properties from entities
join entity_properties
on entities.id = entity_properties.entity_id
where entities.id in (
select entity_id from entity_properties
where value = '6258006d824a25dabdb39a79.pdf'
)
group by entities.id;
what I get is:
[
{
"entity_number":"P1718238009-1",
"entity_properties":"[
\"{\"property_id\":\"006109cd-a100-437c-a683-f13413b448e6\",\"value\":\"Rozilik berildi\"}\",
\"{\"property_id\":\"010f5e23-d66f-4414-b54b-9647afc6762b\",\"value\":\"6258006d824a25dabdb39a79.pdf\"}\",
\"{\"property_id\":\"0a01904e-1ca0-40ef-bbe1-c90eaddea3fc\",\"value\":\"6260c9e9b06e4c2cc492c470_2634467.pdf\"}\"
]"
}
]
As you can see, it is not json parsable
To parse entity_properties as array of objects I need the data in this format
[
{
"entity_number":"P1718238009-1",
"entity_properties":[
{"property_id":"006109cd-a100-437c-a683-f13413b448e6","value":"Rozilik berildi"},
{"property_id":"010f5e23-d66f-4414-b54b-9647afc6762b","value":"6258006d824a25dabdb39a79.pdf"},
{"property_id":"0a01904e-1ca0-40ef-bbe1-c90eaddea3fc","value":"6260c9e9b06e4c2cc492c470_2634467.pdf"}
]
}
]
Can I achieve what I want with ARRAY_AGG()? How?
If not, what approach should I take?

Answer 1

Try using json_agg and json_build_object function
like this:
select
entity_number,
json_agg(json_build_object('property_id', property_id, 'value', value)) entity_properties from entities
join entity_properties
on entities.id = entity_properties.entity_id
where entities.id in (
select entity_id from entity_properties
where value = '6258006d824a25dabdb39a79.pdf'
)
group by entities.id;

Answer 2

Using a simplified sample data this query provides the first step of the aggregation
with tab as (
select * from (values
(1,'a','x'),
(1,'b','y'),
(2,'c','z')
) tab(entity_number,property_id,value)
)
select
entity_number,
json_agg( json_build_object('property_id', property_id, 'value', value)) entity_properties
from tab
group by 1
;
entity_number|entity_properties |
-------------+----------------------------------------------------------------------------+
1|[{"property_id" : "a", "value" : "x"}, {"property_id" : "b", "value" : "y"}]|
2|[{"property_id" : "c", "value" : "z"}]
Additional aggregation returns the final json array
with tab as (
select * from (values
(1,'a','x'),
(1,'b','y'),
(2,'c','z')
) tab(entity_number,property_id,value)
),
tab2 as (
select
entity_number,
json_agg( json_build_object('property_id', property_id, 'value', value)) entity_properties
from tab
group by 1
)
select
json_agg(
json_build_object(
'entity_number',
entity_number,
'entity_properties',
entity_properties
)
)
from tab2
[
{
"entity_number": 1,
"entity_properties": [
{
"value": "x",
"property_id": "a"
},
{
"value": "y",
"property_id": "b"
}
]
},
{
"entity_number": 2,
"entity_properties": [
{
"value": "z",
"property_id": "c"
}
]
}
]
Note that I used jsonb_pretty to format the output.