DATEPART () function returns separate portions date / time, such as year, month, day, hour, minute and so forth.
The DATEDIFF () function returns the time difference between the two dates.
- Find the morning's data the SELECT * from R_Attendance the WHERE ( the datepart of a (hour, RDatetime) > = 0 and the datepart of a (hour, RDatetime) < 12 ) and DATEDIFF (d, RDatetime, GetDate ()) = 0 - Find the afternoon data SELECT * from R_Attendance WHERE ( the datepart (hour, RDatetime) > 12 is and the datepart (hour, RDatetime) <= 23 is ) and DATEDIFF(d,RDatetime,GetDate())=0
Calculating the difference between two time
A difference of a few years: SELECT DATEDIFF (YEAR, '2017-07-01 11:25:52', '2018-07-02 12:25:52'); Results: 1
Difference between the number of days: SELECT DATEDIFF (DAY, '2018-07-01 11:25:52', '2018-07-02 12:25:52'); Results: 1
Difference hours: SELECT DATEDIFF (HOUR, '2018-07-01 11:00:00', '2018-07-01 16:00:00'); Results: 5
A difference of scores: MINUTE, the number of seconds difference: SECOND, a difference of a few months: MONTH
Gets the day, month, and year data:
According to the above calculated time difference, we can obtain results as follows:
当日：SELECT * FROM UserTable WHERE DATEDIFF(DAY, StartTime, GETDATE())=0
当月：SELECT * FROM UserTable WHERE DATEDIFF(MONTH, StartTime, GETDATE())=0
当年：SELECT * FROM UserTable WHERE DATEDIFF(YEAR, StartTime, GETDATE())=0
If you want to get the previous day, month or year, etc., can function only equal to 1, and so can, on the contrary get a month later, and year. Function is equal to -1, not to list here.