select sd business_date decode th tran_type SALE ti qty RETURN -1 ti q

select
    sd.business_date,
             decode(th.tran_type,'SALE',ti.qty,'RETURN',-1*ti.qty,1) count_resa,
    ti.qty, -- <= я добавил
    ti.unit_retail*decode(th.tran_type,'SALE',1,'RETURN',-1,1) sum_resa
  from rms.sa_store_day sd,
       sa_tran_head th,
                                                            sa_tran_item ti
where th.STORE_DAY_SEQ_NO=SD.STORE_DAY_SEQ_NO
  and ti.tran_seq_no=th.tran_seq_no
  and ti.item='23456100005'
  and th.status='P'
  and ti.qty<>1
--  and th.tran_seq_no = 802091002