OACLE判断表是否存在，怎么生成新表

declare IsTable  INTEGER:=0;beginselect count(*) into IsTable from DBA_TABLES where table_name='NEDW_M_B_ADSL_D';if IsTable=0 then   create table NEDW_M_B_ADSL_D as    select * from NEDW_M_B_ADSL_D@lnzd where rownum<=10;else   insert into NEDW_M_B_ADSL_D select * from NEDW_M_B_ADSL_D@lnzd where rownum<=10;end if;end;