Postgresql Convert SQL XML Coding to SQL JSON Coding - sql

Question

How to convert XML SQL Coding to JSON SQL Coding.
Example:
SELECT XMLELEMENT(NAME "ORDER", XMLFOREST(PURCHASE_ORDER AS OD_NO)) AS "XMLELEMENT" FROM
TBL_SALES
Now how to convert this XMLELEMENT & XMLFOREST into JSON functions. Please help me. Do we have equivalent XMLELEMENT/XMLFOREST in JSON functions.
xml:
<order><OD_NO>4524286167</OD_NO><order_date>2020-06-15</order_date><sales_office>CH</sales_office></order>
json:
{ "OD_NO": "4524286167", "order_date": "2020-06-15", "sales_office": "CH" }

Answer 1

Here row_to_json will do the thing.
You can write your query like below:
select row_to_json(x) from
(select purchase_order "OD_NO", order_date, sales_office from tbl_sales ) x
If You want to aggregate all the results in a single JSON Array use JSON_AGG with row_to_json:
select json_agg(row_to_json(x)) from
(select purchase_order "OD_NO", order_date, sales_office from tbl_sales ) x
DEMO

Answer 2

These Postgresql functions
json_build_object(VARIADIC "any") and
jsonb_build_object(VARIADIC "any")
are semantically close to XMLELEMENT and very convenient for 'embroidering' of whatever complex JSON you may need. Your query might look like this:
select json_build_object
(
'OD_NO', order_number, -- or whatever the name of the column is
'order_date', order_date,
'sales_office', sales_office
) as json_order
from tbl_sales;
I do not think that there is a XMLFOREST equivalent however.