Postgres 11

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CREATE TABLE mytable (
    myjson jsonb
);

INSERT INTO mytable VALUES
('[{"ch":"1","id":"12","area":"0","level":"Superficial","width":"","length":"","othern":"5","percent":"100","location":" 2nd finger base"},{"ch":"1","id":"13","area":"0","level":"Skin","width":"","length":"","othern":"1","percent":"100","location":" Abdomen "}]');

SELECT 
    jsonb_pretty(myjson) 
FROM mytable

CREATE TABLE



INSERT 0 1




jsonb_pretty


[
    {
        "ch": "1",
        "id": "12",
        "area": "0",
        "level": "Superficial",
        "width": "",
        "length": "",
        "othern": "5",
        "percent": "100",
        "location": " 2nd finger base"
    },
    {
        "ch": "1",
        "id": "13",
        "area": "0",
        "level": "Skin",
        "width": "",
        "length": "",
        "othern": "1",
        "percent": "100",
        "location": " Abdomen "
    }
]



SELECT 1


CREATE OR REPLACE FUNCTION json_array_update_index(_myjson jsonb, _val_to_change int, _dest_val int)
RETURNS jsonb
AS $$
DECLARE
    _json_output jsonb;
BEGIN
    SELECT 
        jsonb_agg(
             CASE WHEN elems ->> 'othern' = _val_to_change::text THEN
                 jsonb_set(elems, '{othern}', _dest_val::text::jsonb)
             ELSE elems  END
        ) as json_array
    FROM
        jsonb_array_elements(_myjson) elems
    INTO _json_output;
    
    RETURN _json_output;
END;
$$ LANGUAGE 'plpgsql';

CREATE FUNCTION


SELECT 
    jsonb_pretty(new_json) 
FROM 
json_array_update_index(
    '[{"ch":"1","id":"12","area":"0","level":"Superficial","width":"","length":"","othern":"5","percent":"100","location":" 2nd finger base"},{"ch":"1","id":"13","area":"0","level":"Skin","width":"","length":"","othern":"1","percent":"100","location":" Abdomen "}]', 
    5, 
    7
) AS new_json


jsonb_pretty


[
    {
        "ch": "1",
        "id": "12",
        "area": "0",
        "level": "Superficial",
        "width": "",
        "length": "",
        "othern": 7,
        "percent": "100",
        "location": " 2nd finger base"
    },
    {
        "ch": "1",
        "id": "13",
        "area": "0",
        "level": "Skin",
        "width": "",
        "length": "",
        "othern": "1",
        "percent": "100",
        "location": " Abdomen "
    }
]



SELECT 1