declare  
  -- 指向所有 table 的游标  
  cursor c_t is   
    select table_name  
    from user_tables;  
    
  table_name user_tables.table_name%type;  
begin  
  open c_t;  
  loop   
       fetch c_t into table_name;   
       exit when c_t%notfound;  
         
       -- 用 delete 而不用 truncate 是为了能户用户回滚,减少误操作  
       execute immediate 'delete from ' || table_name;  
  end loop;  
  close c_t;  
end;