More CASE and DECODE in oracle SQL

SELECT b.TARIKH,
b.KOD_PROJEK,
a.NAMA_PROJEK,
b.KOD_VOT, 
b.DASAR,
b.KET,
(select d.NAMA_TRANS from sbp_trans d where d.JENIS = b.JENIS_TRANS) as trans,
b.LO as rujukan,
(case when b.jenis_trans in (3,4) then b.amaun
else null
end) as debit,
DECODE(b.JENIS_TRANS, 5, b.AMAUN, null) as kredit,
(case when b.jenis_trans not in (1,2,6) then null
else b.AMAUN
end) as amt_col8, 
b.JENIS_TRANS,
(select c.AMAUN from sbp_budget c where c.KOD_VOT = b.kod_vot and c.DASAR = b.dasar and c.PTJ = a.PTJ and c.SPTJ = a.SPTJ
and c.thn_blj = :as_thnblj and c.JENIS = 1) as peruntukan,
b.KOD_SODO
FROM PROJEK a, BELANJA b
WHERE b.KOD_VOT like :as_vot
AND b.DASAR like :as_dasar
AND a.KOD_PROJEK = b.KOD_PROJEK
AND substr(a.KOD_PROJEK, 1,4) = :as_thnblj
AND a.PTJ = :as_ptj
AND a.SPTJ like :as_sptj