sql 语句中between and 查询， 时间参数如何传递？

Question

var date1,date2:TDateTime;……Date1 := EncodeDate(year, month, 1);Date2 := EncodeDate(year, month, 31);query.SQL.Add('select * from sxdj where sxsj between date1 and date2');这样为什么不可以？然后我试了一下这种query.SQL.Add('select * from sxdj where sxsj between :date1 and :date2);parameters.parambyname('date1).value:=EncodeDate(year, month, 1);parameters.parambyname('date2').value:=EncodeDate(year, month, 31);error ：object or class type requiredmissing operator or semicolon