SQL日期查询与比较方法

datediff(day, {d '1900-01-01'},_date)  between  Datediff(day, {d '1900-01-01'},_date1)  and Datediff(day, {d '1900-01-01'},_date2)；
 

Datediff(second, {d '1900-01-01'},datetime1)=Datediff(second, {d '1900-01-01'},datetime 2)；