查询系统表，判断表是否存在，存在则直接删除

select count(*)	from user_objects where object_name=upper(p_table_name);
select count(*) from user_tables where table_name=upper(p_table_name);

create or replace procedure p_drop_table_if_exist_v1(
p_table_name in varchar2
) is
v_count number(10);
begin
select count(*)
into v_count
from user_objects
where object_name=upper(p_table_name);
if v_count > 0 then
execute immediate 'drop table ' || p_table_name || ' purge';
end if;
exception
when no_data_found then
    begin
        null;
    end;
end;
/ 

create or replace procedure p_drop_table_if_exist_v2(
p_table_name in varchar2
) is
v_table_name varchar2(20);
begin
select table_name 
into v_table_name 
from user_tables 
where table_name=upper(p_table_name);
if length(v_table_name)>0 then  
execute immediate 'drop table ' || p_table_name || ' cascade constraints'; 
end if;

exception
when no_data_found then
    begin
        null;
    end;
end;
/