>I need to replace an apostrophe with an empty string. How do I do that? This gives an error.
>

>SET @DocumentName = REPLACE(@DocumentName,'''','')	
>

declare @Doc varchar(max)
set @Doc = 'test''test'
set @doc = replace(@Doc,quotename(''''),'')
set @Doc = 'test''test'
set @doc = replace(@Doc,'''','')
select @doc

You're missing one extra '