How to get a json object as column values using postgresql?

Question

I have a data like below

id | customer  | region   | circle
----------------------------------
 1 | airtel    | tn       | c1
 2 | reliance  | ap       | c2

I am expecting the json output like below using PostgreSQL

JSON

[
    {"id":"1_airtel","parent":"#","text":"airtel"},
    {"id":"1_airtel_tn","parent":"1_airtel","text":"tn"},
    {"id":"1_airtel_tn_c1","parent":"1_airtel_tn","text":"c1"},
    {"id":"2_reliance","parent":"#","text":"reliance"},
    {"id":"2_reliance_ap","parent":"2_reliance","text":"ap"},
    {"id":"2_reliance_ap_c2","parent":"2_reliance_ap","text":"c2"}
]

Answer 1

One option uses a lateral join to generate the rows, and then json function to_jsonb() to turn them to object. The final step is aggregation:

select jsonb_agg(to_jsonb(v)) res
from mytable t
cross join lateral (values
    (
        concat_ws('_', id::text, customer), 
        '#', 
        customer
    ),
    (
        concat_ws('_', id::text, customer, region), 
        concat_ws('_', id::text, customer), 
        region
    ),
    (
        concat_ws('_', id::text, customer, region, circle), 
        concat_ws('_', id::text, customer, region), 
        circle
    )
) v(id, parent, text)

Demo on DB Fiddle