Select Unique value from a JSON Array - PostgreSQL JSON column - sql

Question

I have the following JSON document stored in a PostgreSQL JSON column:
{
"status": "Success",
"message": "",
"data": {
"serverIp": "XXXX",
"ruleId": 32321,
"results": [
{
"versionId": 555555,
"PriceID": "8abf35ec-3e0e-466b-a4e5-2af568e90eec",
"price": 350,
"Convert": 0.8,
"Cost": 15
"Customer_ID":1
},
{
"versionId": 4444,
"PriceID": "b5a1dbd5-17b4-4847-8b3c-da334f95276a",
"price": 550,
"Convert": 0.7,
"Cost": 10,
"Customer_ID":10
}
]
}
}
I am trying to retrieve the price for specific customer_ID
I am using this query to get the price for Customer_ID=1
select json_array_elements(t.info -> 'data' -> 'results') ->> 'price'
from mytable t
where exists (
select
from json_array_elements(t.info -> 'data' -> 'results') x(elt)
where (x.elt ->> 'Customer_ID')::int = 1
)
The problem is that i am getting the same results for Customer_ID=1 and for Customer_ID=10
I am basically getting both elements of the array instead of just one.
I don't know what i am doing wrong

Answer 1

You can use a lateral join to unnest the array elements, and then filter on the customer with a where clause; this leaves you with just one row, from which you can extract the price:
select x.elt ->> 'price' price
from mytable t
cross join lateral json_array_elements(t.info -> 'data' -> 'results') x(elt)
where x.elt ->> 'Customer_ID' = 1
Note that you don't need to cast the customer id to an int, as it is already stored in the proper format in the json array.