SQL - Ayuda CASE

CASE WHEN B.LEEMOBLE IN(402,403,404) THEN 'SI' ELSE 'NO' END AS APORTA

mysql> SELECT * FROM tabla;

+------+-------------+

| id   | observacion |

+------+-------------+

| 1    | NULL        |

| 2    | 4000        |

| 2    | 4002        |

| 3    | 4003        |

| 4    | 4000        |

| 4    | 4001        |

+------+-------------+

6 rows in set (0.00 sec)

mysql> SELECT

    ->   id, observacion,

    ->   CASE WHEN exists ( SELECT id

    ->                      FROM tabla T2

    ->                      WHERE T2.id = T1.id AND

    ->                      observacion in (4002, 4003, 4004))

    ->   THEN 'SI' ELSE 'NO' END aporta

    -> FROM tabla T1;

+------+-------------+--------+

| id   | observacion | aporta |

+------+-------------+--------+

| 1    | NULL        | NO     |

| 2    | 4000        | SI     |

| 2    | 4002        | SI     |

| 3    | 4003        | SI     |

| 4    | 4000        | NO     |

| 4    | 4001        | NO     |

+------+-------------+--------+

6 rows in set (0.00 sec)