set head off;
set feed off;
spool /home/up.sql;
select 'drop table ' || table_name ||';'||chr(13)||chr(10) from user_tables;
spool off;
set feed off;
spool /home/up.sql;
select 'drop table ' || table_name ||';'||chr(13)||chr(10) from user_tables;
spool off;
生成文件，然后执行@up.sql即可