下面的语句有什么东东，如何修改

下面的语句有什么错误，怎么修改
pb连的oracle库
 to_char(b.cshsj, 'yyyy.mm.dd') <= c_endsj and to_char(b.cshsj, 'yyyy.mm.dd') >= c_startsj 


------解决方案--------------------
to_char(b.cshsj, 'yyyy.mm.dd') <= :c_endsj and to_char(b.cshsj, 'yyyy.mm.dd') >= :c_startsj
------解决方案--------------------

探讨

to_char(b.cshsj, 'yyyy.mm.dd') <= :c_endsj and to_char(b.cshsj, 'yyyy.mm.dd') >= :c_startsj