Use a UDF as the default value in a table column in SQL Server

Question

I created a scaler UDF (called sCurrentAppUser()) in SQL Server 2012 Express and I would like to use this UDF as a default value when defining a table. But every time I try, I get an error of "'sCurrentAppUser' is not a recognized built-in function name."

Since I can't post more than two links yet (reputation), I'll link to my research and references in a comment.

Here's my UDF:

ALTER FUNCTION [dbo].[sCurrentAppUser] ()
RETURNS nVarChar(128)
AS BEGIN
   DECLARE @CurrentAppUser nVarChar(128)

   IF EXISTS (SELECT 1 FROM ActiveConnections WHERE ComputerName = host_name ()) BEGIN
      SELECT   @CurrentAppUser = CONVERT (nVarChar(128), LoginUser)
      FROM     ActiveConnections
      WHERE    ComputerName = host_name ()

   END ELSE BEGIN
      SELECT   @CurrentAppUser = Convert (nVarChar(128), suser_sname ())
      WHERE    NOT EXISTS (
                  SELECT   1
                  FROM     ActiveConnections
                  WHERE    ComputerName = host_name ()
               )

   END

   RETURN @CurrentAppUser

END

And my attempt at creating the table with the default constraint on the first column:

CREATE TABLE [dbo].[Clients](
   [ModifyingUser] [nvarchar](128) NOT NULL DEFAULT sCurrentAppUser (),
   [Modification] [char](1) NULL DEFAULT 'A',
   [ModifyingHost] [nvarchar](128) NOT NULL DEFAULT host_name (),
   [ClientID] [uniqueidentifier] NOT NULL,
   [Label] [nvarchar](1024) NULL,
   CONSTRAINT [PK_Clients] PRIMARY KEY (
      [ClientID] ASC
   )
)

Pique

This page specifically says "You can use scalar-valued UDFs as the default value for a column in a table." The MSDN documentation doesn't say anything about not being able to do it. – Pique

This forum thread gives example syntax, treating it like a computed column instead of a default constraint, but that doesn't work for me either. And this StackExchange question talks about using a parameterized UDF as the default constraint, but the "answer" talks about not using a UDF at all. – Pique

Answer 1

You should add schema name for that function:

CREATE TABLE [dbo].[Clients](
   [ModifyingUser] [nvarchar](128) NOT NULL DEFAULT dbo.sCurrentAppUser (),
   [Modification] [char](1) NULL DEFAULT 'A',
   [ModifyingHost] [nvarchar](128) NOT NULL DEFAULT host_name (),
   [ClientID] [uniqueidentifier] NOT NULL,
   [Label] [nvarchar](1024) NULL,
   CONSTRAINT [PK_Clients] PRIMARY KEY (
      [ClientID] ASC
   )
)

Pentavalent

Marked as solved. I just wish I could give you more kudos than that for a quick and correct answer. Thanks! – Pique

you mean using dbo.sCurrentAppUser() instead of sCurrentAppUser(), nice.. – Conferral