Oracle 21c

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CREATE TABLE runtime (
  ROOM_LIGHT varchar(20),
  STARTE int,
  ENDE int,
  RUNNING int
);
insert into runtime
Select '01', 10, 4, 5 from dual union all
Select '02', 10, 4, 5 from dual union all
select '01', 10, 14, 5 from dual;
3 rows affected

SELECT ROOM_LIGHT, 
        JSON_OBJECT(
          'ROOM_LIGHT : ' || ROOM_LIGHT value
          JSON_ARRAYAGG(
           JSON_OBJECT (
             'START' VALUE STARTE,
             'ENDE' VALUE ENDE,
             'RUNE' VALUE RUNNING
           )
          )
         ) as json
FROM runtime
GROUP BY ROOM_LIGHT;


ROOM_LIGHT
JSON


01
{"ROOM_LIGHT : 01":[{"START":10,"ENDE":4,"RUNE":5},{"START":10,"ENDE":14,"RUNE":5}]}

02
{"ROOM_LIGHT : 02":[{"START":10,"ENDE":4,"RUNE":5}]}

ROOM_LIGHT	JSON
01	{"ROOM_LIGHT : 01":[{"START":10,"ENDE":4,"RUNE":5},{"START":10,"ENDE":14,"RUNE":5}]}
02	{"ROOM_LIGHT : 02":[{"START":10,"ENDE":4,"RUNE":5}]}