SQL Server 2008 - How do i return a User-Defined Table Type from a Table-Valued Function?

Even though you can not return the UDTT from a function, you can return a table variable and receive it in a UDTT as long as the schema match. The following code is tested in SQL Server 2008 R2

-- Create the UDTT

CREATE TYPE dbo.MyCustomUDDT AS TABLE
(
    FieldOne varchar (512),
    FieldTwo varchar(1024)
)

-- Declare your variables

DECLARE @uddt MyCustomUDDT;
DECLARE @Modifieduddt MyCustomUDDT;

// Call the function

INSERT INTO @Modifieduddt SELECT * FROM dbo.MyUDF(@uddt);

Function signature

CREATE FUNCTION dbo.MyUDF(@localUDDT MyCustomUDDT)
RETURNS @tableVar TABLE
(
    FieldOne varchar (512),
    FieldTwo varchar(1024)
)
AS
BEGIN
 --Modify your variable here
RETURN
END

Hopefully this will help somebody.

Ok - so it cant be done.

Easy enough to duplicate the table definition in the return type (with the use of scripting).

Still - hopefully this issue gets rectified in the next version of SQL Server.

The syntax for CREATE FUNCTION indicates that the only way to define a table return type is by listing columns and types, a <table_type_definition>. Even SQL Server "Denali" has the same definition for <table_type_definition>. Although strangely, it's syntax doesn't include multi-statement Table valued functions, or anything else that references this fragment.