select 'alter table '||owner || '.' || table_name || ' allocate extent;' from  all_tables  where owner in (select t.username from all_users t where username like '%FQ3%') and  NUM_ROWS = 0 and Table_Name like 'T_%';

* 把上面sql中的FQ3换成自己的库后缀后执行sql，执行后是一组sql，拷贝出来都执行一遍再重新备份即可