SELECT name, json_array_elements(myjson)->>'id' id FROM
(SELECT 'Dingsda'::text AS name, json_build_array('{"id" : 100}'::json, '{"id" : 200}'::json) myjson
  UNION ALL
 SELECT 'Dingsbums'::text AS name, json_build_array('{"id" : 101}'::json, '{"id" : 201}'::json, '{"id" : 301}'::json) myjson
) t;

+-----------+-----+
|   name    | id  |
+-----------+-----+
| Dingsda   | 100 |
| Dingsda   | 200 |
| Dingsbums | 101 |
| Dingsbums | 201 |
+-----------+-----+

+-----------+-----+-------+
|   name    | id  | index |
+-----------+-----+-------+
| Dingsda   | 100 |     0 |
| Dingsda   | 200 |     1 |
| Dingsbums | 101 |     0 |
| Dingsbums | 201 |     1 |
| Dingsbums | 301 |     2 |
+-----------+-----+-------+