为什么加了between and后比没有加使得数据统计会更大，比如我有个表s查询得出
select sum(a) from s where f between 0 and 9999 比select sum(a)from s还要大,f是最大范围
原句是
select sum(a) from s where f between 0 and 9999and c'' and k between '2007-1-1' and '2008-2-2'and t=yyy
与select sum(a) from s wherec'' and k between '2007-1-1' and '2008-2-2' and t=yyy
还有申明:尽管f为无穷大的范围还是这样,理论上结果应该一样,但是我的不是
