关于sql时间类型字段查询的有关问题

关于sql时间类型字段查询的问题
请问一下,谁能告诉我,这三条sql为什么前两条能查询出数据,第三条不行呢,可以确定表中dtTime字段有等于2012-02-25 10:29:09的数据,可为什么查询不出来,也没提示出错,就是查不到数据而已

rs.Open "select * from ssUser where dtTime > convert (DateTime,'" & "2012-02-25 10:29:09" & "')", cn, adOpenStatic, adLockOptimistic

rs.Open "select * from ssUser where dtTime < convert (DateTime,'" & "2012-02-25 10:29:09" & "')", cn, adOpenStatic, adLockOptimistic

rs.Open "select * from ssUser where dtTime = convert (DateTime,'" & "2012-02-25 10:29:09" & "')", cn, adOpenStatic, adLockOptimistic

表如图:


------解决方案--------------------
如果是sql server,则可如下:
select * from ssUser where convert(varchar(19),dttime,120) = '2012-02-25 10:29:09'
或者
select * from ssUser where datediff(ss,dttime,'2012-02-25 10:29:09') = 0