问使用sum语句时出现的group by函数问题

EN

 SELECT DISTINCT abc_value,
           COUNT (*) AS num_abc_values
    from   (
     select dsp_sku,
     sum(case
        when EXPTD_QTY <> ACTL_INVN_QTY then (EXPTD_QTY-ACTL_INVN_QTY)*(-1)
        else null
      end) as "Variance_"
    ,decode (cc.stat_code, '0', 'Unprocessed', '90', 'Processed', '99', 'Expired') as Status,
    trunc(cc.create_date_time) CC_date,
      case
        when dsp_sku = 'EGIA60AMT' then 'A'
        when dsp_sku = 'LF1937' then 'A'
        when dsp_sku = '980X3ENDIUU' then 'A'
        when dsp_sku = '186-0106' then 'A'
        when dsp_sku = 'PM35MN02' then 'A'
     when dsp_sku = 'SIGC60MT' then 'B'
        when dsp_sku = 'GS833' then 'B'
        when dsp_sku = '5.5 PED' then 'B'
        when dsp_sku = 'L74' then 'B'
        when dsp_sku = 'VLOCL2105' then 'B'
        when dsp_sku = 'VLOCM0134' then 'C'
        when dsp_sku = '8886471021V' then 'C'
        when dsp_sku = 'SILSCLINCH46' then 'C'
     when dsp_sku = 'YCN1800P' then 'D'
        when dsp_sku = 'YCN1801P' then 'D'
        when dsp_sku = 'Y-REFACH-X-E' then 'D'
        when dsp_sku = 'ZL7777-0091' then 'D'
        else 'Empty Location'
      end as ABC_Value
    from WH_GHC1.CYCLE_COUNT_HIST cc
      left join item_master im on
        im.sku_id = cc.sku_id
      inner join locn_hdr lh on
        lh.locn_id = cc.locn_id
    where
      cc.whse = 'PH3'
      --and cc.stat_code in ('0','90') --stat_code: 0 is unprocessed, 90 is processed, 99 is expired
      and cc.stat_code = 90
      --and cc.stat_code = 0
      --and cc.create_date_time between '&FromDate' and '&EndDate'

      and cc.create_date_time between '&FromDate' and '&ToDate'
    --and dsp_sku = '&SKU'
      --and not im.srl_nbr_reqd = 4
      --and EXPTD_QTY = 0
      --and actl_invn_qty = 0
      )
    GROUP BY ABC_Value, Dsp_sku
    --having count (Variance_) <>0;