只从DateTime (SQL函数)获取日期部分

这两个函数哪个更有效?toDate1或toDate2——有更好的吗?

use Something
go
-- All SQL versions
create function toDate1(@t datetime)  
    returns datetime as begin  
    declare @return datetime  
    select  @return = dateadd(day,datediff(day,0,@t),0)
    return  @return end
go
-- SQL 2008 ->
create function toDate2(@t datetime)  
    returns datetime as begin  
    declare @return datetime  
    select  @return = convert(date, @t) 
    return  @return end

SELECT convert(date, cast ('2014-01-01 10:11:12' as datetime), 106)