orale已存在的表和SEQUENCE查询和删除

orale 已存在的表和 SEQUENCE 查询和删除 

declare       num   number; begin       select count(1) into num   from all_tables where TABLE_NAME = 'TU_DIS_ES_COMMISSION_HIST' ;      if   num=1   then           execute immediate 'drop table TU_DIS_ES_COMMISSION_HIST';       end   if;             			select  count(1) into num  from  user_sequences  where  sequence_name= UPPER('seq_dis_es_commission_hist');             if   num=1   then           execute immediate 'drop SEQUENCE seq_dis_es_commission_hist';       end   if;       end; /