Parsing JSON data with LOOP - json

Question

I am parsing data from JSON with UNION ALL, but I need repeated it more times. Try to use LOOP, but it doesn't works. :(
I need to parse every element from array in JSON to rows from statements.
I change the number of element in: statements::json->0 and than UNION the data.
The CODE I want to replace with some LOOP:
(
SELECT
execution_entry_id,
account,
trim('"' FROM (account::json->'startBalance')::text) AS startBalance,
trim('"' FROM (account::json->'endBalance')::text) AS endBalance
FROM (
SELECT
execution_entry_id,
statements::json->0 AS account
FROM(
SELECT
e.id AS execution_entry_id,
response_body,
response_body::json->'statements' AS statements
FROM stage_cz.cb_data_execution_entry e
LEFT JOIN stage_cz.cb_data_execution_entry_details d
ON d.execution_entry_id = e.id
WHERE provider_name = 'sokordiatech'
) a
) b WHERE account IS NOT NULL
)
UNION ALL
(
SELECT
execution_entry_id,
account,
trim('"' FROM (account::json->'startBalance')::text) AS startBalance,
trim('"' FROM (account::json->'endBalance')::text) AS endBalance
FROM (
SELECT
execution_entry_id,
statements::json->1 AS account
FROM(
SELECT
e.id AS execution_entry_id,
response_body,
response_body::json->'statements' AS statements
FROM stage_cz.cb_data_execution_entry e
LEFT JOIN stage_cz.cb_data_execution_entry_details d
ON d.execution_entry_id = e.id
WHERE provider_name = 'sokordiatech'
) a
) b WHERE account IS NOT NULL
)
I try to use:
do $$
declare
counter integer := 0;
begin
while counter < 10 loop
SELECT
execution_entry_id,
statements::json->counter AS account
FROM(
SELECT
e.id AS execution_entry_id,
response_body,
response_body::json->'statements' AS statements
FROM stage_cz.cb_data_execution_entry e
LEFT JOIN stage_cz.cb_data_execution_entry_details d
ON d.execution_entry_id = e.id
WHERE provider_name = 'sokordiatech'
) a;
counter := counter + 1;
end loop;
end$$;
and it ends with error:
ERROR: query has no destination for result data
Hint: If you want to discard the results of a SELECT, use PERFORM instead.
Where: PL/pgSQL function inline_code_block line 6 at SQL statement
1 statement failed.
It's possible to get data with LOOP or how instead of 10x UNION ALL, please?
Thanks.

Answer 1

If you are use statements::json->0, so you have Json array in your Json string. For splitting array elements from Json array, you can use jsonb_array_elements_text function on PostgreSQL, this function will be extracting your array elements like as rows. For do this you don't need using loop. For example:
with tbl as (
select
'[
{
"employee_id": 2,
"full_name": "Megan Berry",
"manager_id": 1
},
{
"employee_id": 3,
"full_name": "Sarah Berry",
"manager_id": 1
},
{
"employee_id": 4,
"full_name": "Zoe Black",
"manager_id": 1
},
{
"employee_id": 5,
"full_name": "Tim James",
"manager_id": 1
},
{
"employee_id": 6,
"full_name": "Bella Tucker",
"manager_id": 2
}
]'::jsonb as jsondata
)
select jsondata->1 from tbl;
Result:
{"full_name": "Sarah Berry", "manager_id": 1, "employee_id": 3}
This is getting second element of Json array.
But you need all elements, for getting all elements and extracting key values use this syntax:
with table1 as (
select
'[
{
"employee_id": 2,
"full_name": "Megan Berry",
"manager_id": 1
},
{
"employee_id": 3,
"full_name": "Sarah Berry",
"manager_id": 1
},
{
"employee_id": 4,
"full_name": "Zoe Black",
"manager_id": 1
},
{
"employee_id": 5,
"full_name": "Tim James",
"manager_id": 1
},
{
"employee_id": 6,
"full_name": "Bella Tucker",
"manager_id": 2
}
]'::jsonb as jsondata
)
select
tb1.a1->>'full_name' as fullname,
tb1.a1->>'manager_id' as managerid,
tb1.a1->>'employee_id' as employeeid
from (
select jsonb_array_elements_text(jsondata)::jsonb as a1 from table1
) tb1
Result:
fullname managerid employeeid
Megan Berry 1 2
Sarah Berry 1 3
Zoe Black 1 4
Tim James 1 5
Bella Tucker 2 6