Date Calculation – SQL Server Syntax Example: Date Calculation – T-SQL Example

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Date Calculation – SQL Server Syntax Example: Date Calculation – T-SQL Example

Purpose: – Illustrates the SQL Server syntax for the Date Calculation.

SYNTAX:
DATEADD (datepart , number, date ) – Returns a specified date with the specified number interval (signed integer) added to a specified datepart of that date.

* User-defined variables are valid for number and date can be an expression, column expression, user-defined variable, or string literal.

* If the expression is a string literal, it must resolve to a datetime.

* The return data type is the data type of the date argument, except for string literals.

* The return data type for a string literal is datetime. An error will be raised if the string literal seconds scale is more than three positions (.nnn) or contains the time zone offset part.

* Addition for a datepart of microsecond or nanosecond for date data types smalldatetime, date, and datetime is not allowed.

DATEDIFF ( datepart , startdate , enddate ) – Returns the count (signed integer) of the specified datepart boundaries crossed between the specified startdate and enddate.


PURPOSE: DATEADD and DATEDIFF can be used to perform date calculations on date and time datatypes. DATEADD can be used to add to or subtract from a date while DATEDIFF can be used to find the difference between two dates.

Other Excellent Examples of Date Calculations:

1. DATEADD – MSDN
2. DATEDIFF – MSDN
3. SYSTEMDATETIME – MSDN
4. Add a value to a Date – java2s
5. Examples of How to Calculate Different SQL Server Dates – databasejournal
6. SQL Server Date Math – databasejournal

Code Sample for Date Calculation:

 T-SQL | 
 copy code |
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  /*
 Date Calculation example from http://idealprogrammer.com 
 PURPOSE: DATEADD and DATEDIFF can be used to perform date calculations on  
          date and time datatypes.  DATEADD can be used to add to or subtract
          from a date while DATEDIFF can be used to find the difference between 
          two dates.
  Here is a list of date and time data types:
			# date
			# time(n)             maximum scale of 7 (.1234567)
			# datetime            maximum scale of 3 (.123)
			# smalldatetime
			# datetimeoffset(n)   maximum scale of 7 (.1234567)
			# datetime2           maximum scale of 7 (.1234567)       
 SYNTAX: DATEADD (datepart , number, date ) - - Returns a specified date with the
         specified number interval (signed integer) added to a specified datepart 
         of that date.
		* User-defined variables are valid for number and date can be an expression, 
		 column expression, user-defined variable, or string literal.
		* If the expression is a string literal, it must resolve to a 
		 datetime. 
		* The return data type is the data type of the date argument, 
		 except for string literals.
		* The return data type for a string literal is datetime. An error will be 
		 raised if the string literal seconds scale is more than three positions (.nnn)
	     or contains the time zone offset part.
	    * Addition for a datepart of microsecond or nanosecond  for date data types 
	     smalldatetime, date, and datetime is not allowed.
         
 SYNTAX: DATEDIFF ( datepart , startdate , enddate ) - Returns the count 
         (signed integer) of the specified datepart boundaries crossed between 
         the specified startdate and enddate.
        
 NOTES:  DATEADD and DATEDIFF can be used in the SELECT list, WHERE, HAVING, 
         GROUP BY and ORDER BY clauses.
 
 Here is a list of dateparts:
  datepart	 Abbreviations
  year         yy, yyyy
  quarter      qq, q
  month        mm, m
  dayofyear    dy, y
  day          dd, d
  week         wk, ww
  weekday      dw, w
  hour         hh
  minute       mi, n
  second       ss, s
  millisecond  ms   Milliseconds have a scale of 3 (.123). 
  microsecond  mcs  microseconds have a scale of 6 (.123456)
  nanosecond   ns   nanoseconds have a scale of 9 (.123456789).
  */
 
 
/********************************************************
                      DATEADD Examples
*********************************************************/
 
--1. Example of adding to a datepart
DECLARE @datetime2 datetime2 = '2008-01-01 13:10:10.1234567'
SELECT 'year', DATEADD(year,1,@datetime2)
UNION ALL
SELECT 'quarter',DATEADD(quarter,2,@datetime2)
UNION ALL
SELECT 'month',DATEADD(month,3,@datetime2)
UNION ALL
SELECT 'dayofyear',DATEADD(dayofyear,4,@datetime2)
UNION ALL
SELECT 'day',DATEADD(day,5,@datetime2)
UNION ALL
SELECT 'week',DATEADD(week,6,@datetime2)
UNION ALL
SELECT 'weekday',DATEADD(weekday,7,@datetime2)
UNION ALL
SELECT 'hour',DATEADD(hour,8,@datetime2)
UNION ALL
SELECT 'minute',DATEADD(minute,9,@datetime2)
UNION ALL
SELECT 'second',DATEADD(second,10,@datetime2)
UNION ALL
SELECT 'millisecond',DATEADD(millisecond,11,@datetime2)
UNION ALL
SELECT 'microsecond',DATEADD(microsecond,12,@datetime2)
UNION ALL
SELECT 'nanosecond',DATEADD(nanosecond,13,@datetime2);
 
-- 2. Incrementing datepart so it flows to next level
DECLARE @datetime datetime;
SET @datetime = '2010-06-01 01:01:01.123';
SELECT DATEADD(quarter,7,@datetime);     --2012-03-01 01:01:01.123
SELECT DATEADD(month,15,@datetime);      --2011-09-01 01:01:01.123
SELECT DATEADD(dayofyear,369,@datetime); --2011-06-05 01:01:01.123
 
--3. Using Column or expression for date or number
 
--3.a. Using Column for date
CREATE TABLE #DateTable
    (
    dtBirthdate datetime2
    );
INSERT INTO #DateTable(dtBirthdate)VALUES('2001-05-06 23:59:59.9999999');
INSERT INTO #DateTable(dtBirthdate)VALUES('1994-06-07 00:00:00.0000000');
INSERT INTO #DateTable(dtBirthdate)VALUES('1954-03-07 23:59:59.9999999');
INSERT INTO #DateTable(dtBirthdate)VALUES('1927-04-08 00:00:00.0000000');
 
SELECT DATEADD(year,50,dtBirthdate) as Fifty_years_old
FROM #DateTable;
 
DROP Table #DateTable;
GO
 
--3.b. Using expression for number and system date for date
 
SELECT DATEADD(month,-(6*2), SYSDATETIME());
 
--3.c. Using constants for date and number
 
SELECT DATEADD(year, 1, '2010-05-08 10:54:03.123');
 
/********************************************************
                      DATEDIFF Examples
*********************************************************/
 
--1. Example using column for dates
CREATE TABLE #DateTable
    (
    dtBirthdate date
    ,dtDeathdate date
    );
INSERT INTO #DateTable(dtBirthdate,dtDeathDate)
VALUES('1954-09-11','2036-09-12');
 
SELECT DATEDIFF(year,dtBirthdate,dtDeathdate) as age
FROM #DateTable;
 
DROP Table #DateTable;
GO
 
--2. Using user defined variables for dates
 
DECLARE @startdate date = '1954-09-11';
DECLARE @enddate date = '2010-05-08'; 
SELECT DATEDIFF(day, @startdate, @enddate);
 
--3. Using system function, expression, and constant as date
SELECT DATEDIFF(day, '1954-09-11', GETDATE() + 1);
 
/*Other Excellent Examples of Date Calculations:
 
   1. DATEADD - MSDN:
   http://msdn.microsoft.com/en-us/library/ms186819%28v=SQL.100%29.aspx
   
   2. DATEDIFF - MSDN:
   http://msdn.microsoft.com/en-us/library/ms189794%28v=SQL.100%29.aspx
   
   3. SYSTEMDATETIME - MSDN:
   http://msdn.microsoft.com/en-us/library/bb630353(v=SQL.100).aspx
   
   4. Add a value to a Date - java2s:
   http://www.java2s.com/Code/SQLServer/Select-Query/Addvaluetoadate.htm
   
   5. Examples of How to Calculate Different SQL Server Dates - databasejournal:
   http://www.databasejournal.com/features/mssql/article.php/3076421/Examples-of-how-to-Calculate-Different-SQL-Server-Dates.htm
   
   6. SQL Server Date Math - databasejournal
   http://www.databasejournal.com/features/mssql/article.php/10894_2216011_3/Working-with-SQL-Server-DateTime-Variables-Part-Four---Date-Math-and-Universal-Time.htm
 
*/
 
 
 
 

Sample Output for Date Calculation Example

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