SQL Time Collection

1. Current system date, time
Select GETDATE ()
2. DateAdd returns a new datetime value based on adding a period of time to the specified date
Example: Add 2 days to the date
Select DATEADD (day,2, ' 2004-10-15 ')--return: 2004-10-17 00:00:00.000

3. DateDiff returns the number of date and time boundaries across two specified dates.
Select DateDiff (Day, ' 2004-09-01 ', ' 2004-09-18 ')--return: 17

4. DatePart returns an integer representing the specified date portion of the specified date.
SELECT DATEPART (month, ' 2004-10-15 ')--return 10

5. Datename returns a string representing the specified date part of the specified date
SELECT Datename (Weekday, ' 2004-10-15 ')--return: Friday

6. Day (), month (), year ()--can be compared with datepart

Select Current date =convert (varchar), GETDATE (), 120)
, Current time =convert (varchar (8), GETDATE (), 114)

7. Select Datename (DW, ' 2004-10-15 ')

Select how many weeks of the year =datename (Week,getdate ())
, today is the week of =datename (Weekday,getdate ())

function parameters/Functions
GetDate ()--Returns the current date and time of the system
DateDiff (INTERVAL,DATE1,DATE2)--Returns the difference between Date2 and date1 two dates in interval specified mode date2-date1
DATEADD (interval,number,date)--The date after number is added in the way specified by interval
DatePart (interval,date)---Returns the integer value corresponding to the specified portion of the date, interval
Datename (interval,date)--Returns the string name corresponding to the specified part of the date, interval

The setting values for the parameter interval are as follows:

Value abbreviation (SQL Server) Access and ASP description  
Year yy yyyy years 1753 ~ 9999&N Bsp
Quarter qq q season 1 ~ 4 
Month MM M 1 ~ 12 
Day of the year dy y the number of days of the year, the day of the first month 1-366 
Day dd D, 1-31 
Weekday DW w The number of days of the week, the day of the week 1-7 
Week wk WW Week, week of the year 0 ~ 51  
Hour hh H 0 ~ 23 
Minute Mi N minutes 0 ~ 59 
Second ss s seconds 0 ~ 59 
Millisecond ms -milliseconds 0 ~ 999

In Access and ASP, date () and now () are used to obtain system datetime, where Datediff,dateadd,datepart is also used in Access and ASP, and the usage of these functions is similar

Example:
1.GetDate () for SQL Server:select GetDate ()

2.DateDiff (' s ', ' 2005-07-20 ', ' 2005-7-25 22:56:32 ') returns a value of 514,592 seconds
DateDiff (' d ', ' 2005-07-20 ', ' 2005-7-25 22:56:32 ') returns a value of 5 days

3.DatePart (' W ', ' 2005-7-25 22:56:32 ') returns a value of 2 that is Monday (Sunday is 1, Saturday is 7)
DatePart (' d ', ' 2005-7-25 22:56:32 ') returns a value of 25, or 25th
DatePart (' y ', ' 2005-7-25 22:56:32 ') returns a value of 206 that is the No. 206 Day of the Year
DatePart (' yyyy ', ' 2005-7-25 22:56:32 ') returns a value of 2005 that is 2005

The SQL Server DATEPART () function returns a portion of the SQL Server datetime field.

The syntax for the SQL Server DATEPART () function is:
DATEPART (Portion, datetime)

where datetime is the SQL Server datetime field and the name of the section is one of the following: Ms for Milliseconds
Yy for year
Qq for Quarter of the year
Mm for Month
Dy for the day of the year
Dd for day of the Month
Wk for Week
Dw for the day of the Week
Hh for Hour
Mi for Minute
Ss for Second

--1. Write a function that implements the output time information (March 16, 2009 Monday pm) According to ' date of month, day of the week, morning afternoon '
Select Datename (Yy,getdate ()) + ' year ' +
Datename (Mm,getdate ()) + ' month ' +
Datename (Dd,getdate ()) + ' Day ' +
Datename (Weekday,getdate ()) +
Case when Datename (Hh,getdate ()) < "I ' am ' Else ' PM ' End
--2. Write the function, depending on the input time. The day of the year is output
Select DATEPART (dy,getdate ())
--3. Finding random output characters ' A-Z
Select char (97+abs (Checksum (newid ()))%26)
Select char (97+rand () *26)


Attention:
The ASP compares the time of the SQL statement, where D is the number of days!

Access

SELECT * from [table] where DATEDIFF (' d ', Time field, now ()) =0

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SQL Server

SELECT * from [table] where DateDiff (d, Time field, GetDate ()) =0

SQL Time Collection