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In my previous Posts, I discussed about DATETIMEFROMPARTS. Today, we will discuss one more function introduced in SQL SERVER 2012 namely “DATETIME2FROMPARTS“.

Let me explain its syntax, parameters, purpose and examples in detail.

Syntax :

DATETIME2FROMPARTS ( year, month, day, hour, minute, seconds, fractions, precision )

Parameters :
@Year : A valid integer for year.
@Month : A valid integer for month range from 1-12.
@Day : A valid integer for day range from 1-31. (Depends upon the total number of days in a month)
@Hour : A valid integer for Hour range from 0-23.
@Minutes : A valid integer for Minutes range from 0-59.
@Seconds: A valid integer for Seconds range from 0-59.
@Fractions : A valid integer for Fractions range from 0-9999999.
@Precision : A valid integer for Precision range from 0-7.

Purpose :
This function requires year, month, day, hour, minute, seconds, fractions & precision as a parameter (All parameters are mandatory) and returns a valid datetime2 as a result. If we pass any invalid date and time parts, it will generate an error. Also if we pass NULL values to any of its parameters except Precision parameter, it returns NULL value. If we pass NULL value to Precision parameter it will generate an error.
Let me explain this with simple examples.

Example-1 : DATETIME2FROMPARTS

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=23
Declare @Minute as int=59
Declare @Second as int=59
Declare @Fraction as int=50
Select DATETIME2FROMPARTS( @Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,2)
as [RESULT]
--RESULT
2012-12-31 23:59:59.50

Example-2 : DATETIME2FROMPARTS- With Invalid Date and Time Parts
It will generate an error because only valid date and time parts are allowed as a parameter.

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=25 --- Hour cannot be 25
Declare @Minute as int=59
Declare @Second as int=59
Declare @Fraction as int=50
Select DATETIME2FROMPARTS (@Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,2)
as [RESULT]
--RESULT

Msg 289, Level 16, State 5, Line 23
Cannot construct data type datetime2, some of the arguments have values which are not valid.

Example-3 : DATETIME2FROMPARTS- With NULL Date and Time Parts except Precision parameter
If we pass NULL value to any of its parameter except Precision parameter, it will return NULL value

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=23
Declare @Minute as int=59
Declare @Second as int=NULL ---Pass Seconds as NULL
Declare @Fraction as int=50
Select DATETIME2FROMPARTS( @Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,2)
as [RESULT]
--RESULT

Example-4 : DATETIME2FROMPARTS- @Precision as NULL value
If we pass NULL value to precision parameter of this function, it will generate an error.

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=23
Declare @Minute as int=59
Declare @Second as int=50
Declare @Fraction as int=50
Select DATETIME2FROMPARTS( @Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,NULL)
as [RESULT]
--Result

Msg 10760, Level 16, State 1, Line 23
Scale argument is not valid. Valid expressions for data type datetime2 scale argument are integer constants and integer constant expressions.

Example-5 : DATETIME2FROMPARTS- With Null and Invalid parameters
If we pass NULL and Invalid value to its parameter, it will return NULL as a result.

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=25 ---Hour cannot exceed 23
Declare @Minute as int=59
Declare @Second as int=NULL ---Second parameter as NULL
Declare @Fraction as int=50
Select DATETIME2FROMPARTS( @Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,2)
as [Result]
--Result
NULL

Example-6: DATETIME2FROMPARTS- With missing Fraction if precision is defined
If precision is zero , we cannot define the fraction as well. It should be zero.

Declare @Year as smallint=2012
Declare @Month as smallint = 12
Declare @Day as smallint =31
Declare @Hour as int=23
Declare @Minute as int=59
Declare @Second as int=59
Declare @Fraction as int=50
Select DATETIME2FROMPARTS( @Year,@Month,@Day,@Hour,@Minute,@Second,@Fraction,0) as [RESULT]
as [Result]
--Result

Msg 289, Level 16, State 5, Line 8
Cannot construct data type datetime2, some of the arguments have values which are not valid.

Reference : MSDN

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