Convert Query to TSQL UDF

I'm havin an issue converting a working query to a sql server user defined function.
The function takes two dates and returns a table with the difference between the two in each date part no matter how the dates are formatted.
For example if the dates were 1992-09-06 00:00:00 and 19941212 00:00:00 it would return

years    months   days    hours     minutes
---------   ------------    -------    --------     --------------
   2           3             6         0            0

It also returns a specific part if you specify it as a third parameter.

This query is working perfectly as a stand alone query but when I try to put it into a UDF I get the error message: "Incorrect syntax near 'BEGIN'.

Attached are the working query and the UDF.

Can someone let me know what I'm doing wrong?
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I do not think you are clear on user defined functions.  You need to define what is being returned and then select the values into the defined fields.  I've partly modified the code. You can see where the returns clause needs to describe what is being returned.  (You need to add the types varchar, whatever)    Then down below in The select, you should precede it with an insert so that the results are placed into the returned table structure for the udf to pass back to the code from whence it was called.....  you were almost there. Just that little piece missing.

-- =============================================
-- Author:            
-- Create date: 4/12/2012
-- Description:      Returns date diff parts between 2 given dates
-- =============================================
      @dOne datetime,
      @dDos datetime,
      @thePart varchar(15)
years ....,
BEGIN -- main

      -- Fill the table variable with the rows for your result set
IF @thePart = 'all' OR @thePart = ''
insert into @MyTable
years, months,
      when day(@dOne)>day(@dDos)
      then day(@dDos)+
      else day(@dDos)-day(@dOne)
end as days,

datepart(hour,convert(varchar(10),dateadd(minute,minutes,0),108)) as hours,
datepart(minute,convert(varchar(10),dateadd(minute,minutes,0),108)) as minutes

            when day(@dDos)>=day(@dOne)
            then 0
            else -1
      end as months,
      convert(varchar(8),@dDos,108)) as minutes
            datediff(year,@dOne,@dDos) +
                  when month(@dDos)>=month(@dOne)
                  then 0
                  else -1
            end as years
      ) as t
) as t


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Anthony PerkinsCommented:
In other words, if you want to use your SQL script your UDF cannot be an Inline function as you have coded it, it is to be a Multi-Statement function.
ac, would you say this is an appropriate representation for the two different types of functions?

Inline Function:  This is very simple. The returned table is not explicitly defined. the function is expressed as a basic select statement.

Multi-Statement function: More complicated (and can be less efficient). Must define the table to be returned and populate it's values within your code. Must include a BEGIN/END block.
Anthony PerkinsCommented:
That looks right to me.  Though I would add:  In general and for performance reasons, Multi-statement UDFs should be avoided like the plague. :)

But I think you said that...
Garbonzo_HorowitzAuthor Commented:
Thanks. Sorry for the delay in getting back to this question.
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Query Syntax

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