SQL Server convert NULL to empty string in select *

Question

I need to execute the following:

 SELECT * FROM [MY_TVF](9186)
 FOR XML AUTO, ELEMENTS

And replace all NULL values with an empty string '' to include them in the XML. I know I can spit out the elements with an xsi:nil="true" attribute by setting ELEMENTS XSINIL, but I don't want that.

I found this question: Convert NULL to Empty String SQL Server, where the answer says I can use ISNULL() around my query. I tried it like so:

ISNULL((SELECT * FROM [MY_TVF](9186)),'')
FOR XML AUTO,ELEMENTS

But I can't get it to work. I get the following error:

Msg 102, Level 15, State 1, Line 1 Incorrect syntax near ','.

What can I do to simply replace all NULL values with an empty string so they are included in the XML?

Edit

There is no way to replace the * by column names. There is a reason we use a TVF, there are about 40 columns and they might change over time. My query is just to select everything and return it as XML.

Answer 1

Get out of the habit of SELECT *

See if this works.

SELECT Col1,Col2,Col3,Col4,Col5
FROM
(
SELECT 
ISNULL(Col1,'') Col1,
ISNULL(Col2,'') Col2,
ISNULL(Col3,'') Col3,
ISNULL(Col4,'') Col4,
ISNULL(Col5,'') Col5
FROM [MY_TVF](9186)
) T
FOR XML AUTO,ELEMENTS

Answer 2

I have deleted my previous answer and here is the latest one:

Declare @ColName as Varchar(max)
SEt @ColName=''
SELECT  @ColName= COALESCE( @ColName + ' ISNULL(' +c.name + ','''') ','', '') +
c.name + ', ' 
FROM sysobjects o
JOIN syscolumns c ON o.id = c.id
WHERE o.xtype = 'U'
AND (o.name ='tbName')
SEt @ColName=  ( 'Select ' + SUBSTRING(@ColName,0,LEN(@ColName)-1) + ' FROM tbName')
print @colname
EXEC(@ColName)