反思SQL的or连接词

下午在调试程序的时候一个诡异的现象，删除单据后被删除的单据依然显示在列表中，查看后台数据库，删除标记已经被置为Y。心里一阵纳闷，于是打断点跟踪，将程序加载时拼出来的语句放在SQL里执行了一把，结果还是把已经删除的记录给查出来了；然后就对着那个查询语句做修改，改来改去就是改不正确，明明在查询条件中对删除的字段做了过滤，但是还是能查出来。后来再将过滤条件一个一个添加，然后查询的土方法中终于发现了猫腻，嘿嘿  犯错误很低级 就是在过滤条件中添加了or关键字，但是没有加括号...

犯错的语句：

select *  from aaa 
where Delete!='Y'  
and Date between '2010-11-17 00:00:00' and '2010-12-17 23:59:59' 
and To in (select Stock from StockCtrl where User='106') 
or From in (select Stock from StockCtrl where User='106')  
order by Date desc

修改后的语句

select *  from aaa 
where Delete!='Y'  
and Date between '2010-11-17 00:00:00' and '2010-12-17 23:59:59' 
and (To in (select Stock from StockCtrl where User='106') 
or From in (select Stock from StockCtrl where User='106')) 
order by Date desc

其实要是把语句简化为 select * from aaa where delete = 'N' or 1=1 我想应该很快能定位这个错误