Postgres jsonb query on nested object

Question

My postgres db version: 9.4.4. and I have a table with this structure;

CREATE TABLE product_cust
(
 productid character(2),
  data jsonb,
)

I have records like this in the "data" column;

{"productid":"01","cust": [
        {"cell": ["0000xxx0", "0000xxx1"], "name": "John", "email": ["[email protected]"], "custtype": "c"}, 
        {"cell": ["0000xxx2", "0000xxx3"], "name": "Smith", "email": ["[email protected]"], "custtype": "c"}  
]}

I need to extract all records for "cell" . Expected record will be

["0000xxx0", "0000xxx1","0000xxx2", "0000xxx3"] 

or for "email" ["[email protected]","[email protected]"]

My best effort below has been a two(2) step process and will not scale for x no of "cust" objects;

select (data::json#>'{cust,0}')::json#>'{cell}' from product_cust; //return "0000xxx0", "0000xxx1"
select (data::json#>'{cust,1}')::json#>'{cell}' from product_cust; //return "0000xxx2", "0000xxx3"

I will be most grateful if i can be pointed in the right direction

Answer 1

Use json_agg() and jsonb_array_elements() functions:

select json_agg(cell)
from (
    select jsonb_array_elements(elem->'cell') cell
    from (
        select jsonb_array_elements(data->'cust') elem
        from product_cust
        ) subsub
    ) sub

You can merge two inner subqueries:

select json_agg(cell)
from (
    select jsonb_array_elements(jsonb_array_elements(data->'cust')->'cell') cell
    from product_cust
    ) sub

Group results by productid:

select productid, json_agg(cell)
from (
    select productid, jsonb_array_elements(jsonb_array_elements(data->'cust')->'cell') cell
    from product_cust
    ) sub
group by 1
order by 1