Oracle 18c

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CREATE TABLE my_table( user_id INT, my_json_col CLOB )
INSERT INTO my_table
VALUES( 83,
'{
  "user_name": "Dave",
  "phone_number": "13326415",
  "married": false,
  "age": 18
}')
1 rows affected

DECLARE
  v_js_data     my_table.my_json_col%TYPE;
  v_js_obj      JSON_OBJECT_T;
  v_js_obj_list JSON_KEY_LIST;
  v_title       VARCHAR(4000);
  v_value       VARCHAR(4000);  
BEGIN
  SELECT my_json_col INTO v_js_data FROM my_table WHERE user_id = 83;

  v_js_obj := JSON_OBJECT_T.PARSE(v_js_data);
  v_js_obj_list := v_js_obj.get_keys;

  FOR c IN 1 .. v_js_obj_list.COUNT 
  LOOP
    v_title := v_title||RPAD(v_js_obj_list(c),20,' '); 
    v_value := v_value||RPAD(v_js_obj.GET_STRING(v_js_obj_list(c)),20,' '); 
  END LOOP;  
  DBMS_OUTPUT.PUT_LINE(v_title);
  DBMS_OUTPUT.PUT_LINE(v_value);
END;
/
1 rows affected

dbms_output:
user_name           phone_number        married             age                 
Dave                13326415            false               18                  