UFN_STUDENT_GETENROLLMENTBYDATE

        CREATE function dbo.UFN_STUDENT_GETENROLLMENTBYDATE(
            @STUDENTID uniqueidentifier = null,
            @SCHOOLID uniqueidentifier = null,
            @DATE date = null
        )
        returns uniqueidentifier
        with execute as caller
        as 
        begin
            declare @RETVAL uniqueidentifier

            select @RETVAL = ENROLLMENT.ID
            from dbo.EDUCATIONALHISTORY as ENROLLMENT
            inner join dbo.SCHOOL as SCHOOL on ENROLLMENT.EDUCATIONALINSTITUTIONID = SCHOOL.ID
            inner join dbo.ACADEMICYEAR as AY on ENROLLMENT.EDUCATIONALINSTITUTIONID = AY.SCHOOLID
            where 
                (ENROLLMENT.CONSTITUENTID = @STUDENTID) and
                ((SCHOOL.ID = @SCHOOLID) or (@SCHOOLID is null)) and
                (dbo.UFN_DATE_FROMFUZZYDATE(ENROLLMENT.STARTDATE) <= @DATE) and
                ((dbo.UFN_DATE_FROMFUZZYDATE(ENROLLMENT.DATELEFT) >= @DATE) or (ENROLLMENT.DATELEFT = '00000000')) and
                (AY.BILLINGSTARTDATE <= @DATE) and
                (AY.BILLINGENDDATE >= @DATE)
            return @RETVAL
        end