Manipulating the JSON column and split the values - json

Question

I have the following text in one of my Postgres table as TEXT datatype:
[
{"type": "text", "values": ["General"], "valueType": "string", "fieldType": "text", "value": ["General"], "customFieldId": "ee", "name": "customer_group"},
{"type": "text", "values": ["Vienna"], "valueType": "string", "fieldType": "text", "value": ["Vienna"], "customFieldId": "eU", "name": "customer_city"},
{"type": "text", "values": ["Mario"], "valueType": "string", "fieldType": "text", "value": ["Mario"], "customFieldId": "eZ", "name": "first_name"},
{"type": "text", "values": ["2019-06-30"], "valueType": "date", "fieldType": "text", "value": ["2019-06-30"], "customFieldId": "ea", "name": "created_at_date"}
]
I need to split the values of this TEXT field to columns and rows. For that I have converted the TEXT column to JSON as below:
SELECT CAST( "customFieldValues" as JSON) "customFieldValues" FROM fr.contacts
But when I tried to manipulate this JSON value I'm getting NULL as result.
WITH CTE AS(SELECT CAST( "customFieldValues" as JSON) "customFieldValues" FROM fr.contacts
)
SELECT
"customFieldValues" ->>'customer_city' as dd
FROM CTE
Does anyone have any suggestions on this? How to get the column names and it's values in rows. I want to create a TABLE based on this data.
Any suggestions would be of great help.
below is the expected result,
customer_group customer_city first_name created_at_date
General Vienna Mario 2019-06-30

Answer 1

Disclaimer: It is still not clear:
Why is there one element values and one value? What is the difference?
Why are these elements arrays?
step-by-step demo:db<>fiddle
SELECT
MAX(value) FILTER (WHERE column_name = 'customer_group') AS customer_group,
MAX(value) FILTER (WHERE column_name = 'customer_city') AS customer_city,
MAX(value) FILTER (WHERE column_name = 'first_name') AS first_name,
MAX(value) FILTER (WHERE column_name = 'created_at_date') AS created_at_date
FROM (
SELECT
elems ->> 'name' AS column_name,
elems -> 'value' ->> 0 AS value,
data
FROM
mytable,
json_array_elements(data::json) elems
) s
GROUP BY data
Cast text to json with ::json
Expand the JSON array: One row for each element with json_array_elements()
Getting the value: -> 'value' gets the array, ->> 0 gets the text representation of the first array element (the only one here)
Getting the column: ->> 'name' gets the text representation of the column name
Classical pivot algorithm (turning rows to columns) with the FILTER clause.