为什么下面的代码会出错，请大家帮忙！

[dreamedge]

数据库为Access数据,dtTime1 and dtTime2 为日期时间型字段，我的意图是只显示dtTime1和dtTime2中的时间部分
tSql:='Select dtTime1 As DateTimeToTimeStamp(dtTime1) As 上机时间,DateTimeToTimeStamp(dtTime2) As 下机时间 From tLogs'
+' WHERE (dtTime2>=:Q1) And (dtTime2<=:Q2)'
+' Order By dtTime2';
或者
tSql:='Select dtTime1 As FormatDateTime('HH:MM:SS',dtTime1) As 上机时间,FormatDateTime('HH:MM:SS',dtTime2) As 下机时间 From tLogs'
+' WHERE (dtTime2>=:Q1) And (dtTime2<=:Q2)'
+' Order By dtTime2';
都不行，好象错误都是指函数未定义