请教,为什么这个视图检索的很慢?

CREATE OR REPLACE VIEW CUS_SQ_VEIW AS
SELECT 
       CUSTOMER.ID,  
       CUSTOMER.NAME,  
       CUSTOMER.dsc,
       CUSTOMER.address,
       CUSTOMER.phone,
       CUSTOMER.mobile,
       CUSTOMER.zip,        
       CUSTOMER.TYPE,  
       CUSTOMER.dw,
       CUSTOMER.area_id,  
       CUSTOMER.IRD_NUM,       CURRENT_CUS_IRD.BZ,
       CURRENT_CUS_IRD.FLAG,
       CURRENT_CUS_IRD.Sale_Flag,
       CURRENT_CUS_IRD.Sale_Price,
       CURRENT_CUS_IRD.Ird_Dealer_Id,
       CURRENT_CUS_IRD.IRD_ID,
       CURRENT_CUS_IRD.IC_ID,
       CURRENT_CUS_IRD.USE_STATUS_ID, 
       CURRENT_CUS_IRD.GRP_ID as cus_grp_id, 
       CURRENT_CUS_IRD.mod_date,
       CURRENT_CUS_IRD.ic_flag,
       CURRENT_CUS_IRD.ic_sale_flag,
       CURRENT_CUS_IRD.ic_sale_price,
       CURRENT_CUS_IRD.ic_dealer_id,
   
       IC.IC_NO,  
       IRD.MAC_ADDRESS,
       IRD.corp_id,
       
FROM   IC  ,IRD  ,CUSTOMER  ,  CURRENT_CUS_IRD WHERE  ( current_cus_ird.ic_id =ic.ic_id(+)) 
  and ( ird.ird_id (+) = current_cus_ird.ird_id)  
  and ( CURRENT_CUS_IRD.CUS_ID = CUSTOMER.CUS_ID )说明:
 1.四张表中各有2万多条数据( CUSTOMER是视图 ).
 2.去掉where子句query data要10秒,带where时要90多秒.
  绝对速度和配置有关,但带条件相差9倍是否多了点
  请教各位如何优化,谢谢!