conditional opeartor in a query

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Oracle

Hi,

In the following query, i am stuck how to apply conditional operator.
pls help me out...

The query is

SELECT
         NVL ((SELECT maxdrives
                FROM T4_child apici
               WHERE apici.item_number = b.item_number),
             0
            ) AS drives
     DECODE (SIGN ((SELECT COUNT (*)
                         FROM T1_item  ari
                        WHERE ari.item_number = b. _item_number
                          AND ari.master_id =
                                 (SELECT master_id
                                    FROM T2_master
                                   WHERE rule_name = b.rule_name
                                     AND delete_flag = '0')
                          AND ari.delete_flag = '0'
                          AND ari.item_code = 'Voy')
                     ),
                1, 1,
                DECODE (SIGN ((SELECT COUNT (*)
                                 FROM T3_item aci
                                WHERE aci.box_id = b.box_id
                                  AND aci.slot_number > 0
                                  AND item_code = 'LASH')
                             ),
                        1, 1,
                        0
                       )
               ) AS voy,

   FROM T5_box b, T6_Si p
  WHERE b.order_id = p.order_id

In the above query If Dirves =60 i want to execute following queries based on the condition

DECODE (SIGN ((SELECT COUNT (*)
                          FROM T1_item  ari
                         WHERE ari.item_number = b. _item_number
                           AND ari.master_id =
                                  (SELECT master_id
                                     FROM T2_master
                                    WHERE rule_name = b.rule_name
                                      AND delete_flag = '0')
                           AND ari.delete_flag = '0'
                           AND ari.item_code = 'Voy')
                      ),
                 1, 1,

else

DECODE (SIGN ((SELECT COUNT (*)
                          FROM T1_item  ari
                         WHERE ari.item_number = b. _item_number
                           AND ari.master_id =
                                  (SELECT master_id
                                     FROM T2_master
                                    WHERE rule_name = b.rule_name
                                      AND delete_flag = '0')
                           AND ari.delete_flag = '0'
                           AND ari.item_code = 'Voy')
                      ),
                 1, 1,
                 DECODE (SIGN ((SELECT COUNT (*)
                                  FROM T3_item aci
                                 WHERE aci.box_id = b.box_id
                                   AND aci.slot_number > 0
                                   AND item_code = 'LASH')
                              ),
                         1, 1,
                         0
                        )
                ) AS voy,

Pls let me know how to apply conditional operator, in the query.

TIA.