And, just to complete the picture, here's a CLR scalar function (not in-line!):

CREATE ASSEMBLY [DateTimeExtensions]

AUTHORIZATION [dbo]

FROM 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WITH PERMISSION_SET = SAFE

GO

CREATE FUNCTION dbo.DateTimeFromIntegerParts

(

@Date integer,

@Time integer

)

RETURNS datetime

WITH EXECUTE AS CALLER

AS EXTERNAL NAME [DateTimeExtensions].[UserDefinedFunctions].[DateTimeFromIntegerParts]

GO

Called as so:

SELECT

dbo.DateTimeFromIntegerParts

(

tt.next_run_date,

tt.next_run_time

)

FROM #TestTable AS tt

Test results using Jeff's rig:

Michael's code: 1155ms

CLR function: 859ms

Source code:

using System;

using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions

{

[SqlFunction

(

DataAccess = DataAccessKind.None,

IsDeterministic = true,

IsPrecise = true,

SystemDataAccess = SystemDataAccessKind.None

)

]

public static DateTime DateTimeFromIntegerParts(int Date, int Time)

{

return new DateTime

(

Date / 10000,

Date / 100 % 100,

Date % 100,

Time / 10000,

Time / 100 % 100,

Time % 100

);

}

};