declare @n varchar(40)
set @n = 'Johnson Sr., John Richard'
SELECT LEFT(@n,CHARINDEX(',',@n)-1) LastName,
PARSENAME(REPLACE(STUFF(@n,1,CHARINDEX(',',@n)+1,''),' ','.'),2) FirstName,
PARSENAME(REPLACE(STUFF(@n,1,CHARINDEX(',',@n)+1,''),' ','.'),1) MiddleName
--Jonathan
--Jonathan