``` qs = QS(db) ....中间无任何条件操作语句 qs.wheres = ((F.oid > 10) & (F.oid < 100) & qs.wheres) 此时查看qs.wheres.sql出错 ``` 另见:https://github.com/jacktan1991/smartsql/commit/ea5ff81513b5b01e7bb9631650687f113ab36d34#commitcomment-17171486