Get specific value from json field based on last created_at date - sql

Question

I am using retool, which uses AlaSQL to query JSON, trying to get the value from a field that has multiple items; I only want to return the value of the field stock for the key with the latest created_at date.
select tracked_products
from {{ean.data}}
where created_at=(select MAX(created_at) from {{ean.data}});
I can actually get to the fields I want to like this but I do not understand how to filter further
select tracked_products
from {{ean.data}}
where price < 40
result from above query in plain text
[
{
"id": 172165913,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 39.99,
"status": "success",
"created_at": "2022-12-16T12:12:26.000000Z",
"updated_at": "2022-12-16T12:12:26.000000Z"
},
{
"id": 173409443,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-17T03:15:58.000000Z",
"updated_at": "2022-12-17T03:15:58.000000Z"
},
{
"id": 174659591,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-18T16:22:45.000000Z",
"updated_at": "2022-12-18T16:22:45.000000Z"
},
{
"id": 175895075,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-19T03:18:53.000000Z",
"updated_at": "2022-12-19T03:18:53.000000Z"
},
{
"id": 177134025,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-20T15:35:48.000000Z",
"updated_at": "2022-12-20T15:35:48.000000Z"
},
{
"id": 178391290,
"offer_data_id": 2208536,
"stock": 2,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-21T03:09:22.000000Z",
"updated_at": "2022-12-21T03:09:22.000000Z"
},
{
"id": 179654380,
"offer_data_id": 2208536,
"stock": 1,
"sold": 1,
"revenue": "34.99",
"price": 34.99,
"status": "success",
"created_at": "2022-12-22T03:13:50.000000Z",
"updated_at": "2022-12-22T03:13:50.000000Z"
},
{
"id": 180918092,
"offer_data_id": 2208536,
"stock": 1,
"sold": 0,
"revenue": "0.00",
"price": 34.99,
"status": "success",
"created_at": "2022-12-23T03:19:42.000000Z",
"updated_at": "2022-12-23T03:19:42.000000Z"
}
]

Answer 1

try this :
SELECT DISTINCT
(array_agg(j->>'stock') OVER (PARTITION BY tracked_products ORDER BY j->>'created_at' DESC)[1] AS stock
FROM ean.data
CROSS JOIN LATERAL jsonb_path_query(tracked_products :: jsonb, '$[*]') AS j
WHERE price < 40
This query relies on a text sorting on created_at which should be compliant with the actual date format of this text field.
jsonb_path_query is used instead of json_array_elements so that to avoid an error when tracked_products is not a json of type array.
see dbfiddle
Refer to the manual for more info about json manipulation