removing partial string from column

how do i update a table which has like two strings in 1 column like

blog, joe ?

i want to strip the joe into a new field and the blog into another field

update Agency
set firstname= substring(firstname,charindex(' ',firstname)+1 ,len(firstname))

i managed to strip the first name which is the string at the back but not the last name which is the string at the frontTry this to get the lastname:
lastname = left(column1, patindex('%,%', column1) - 1)|||The error message was :-

update Agency
set lastname = left(lastname, patindex('%,%', lastname) - 1)

Server: Msg 536, Level 16, State 3, Line 1
Invalid length parameter passed to the substring function.
The statement has been terminated.

Dario D'Alessandro, Dario
Stan Dickson, Stan
Ray John, Ray
Juan Sanchez, Juan

I trying to remove the Dario|||Gotta make sure there is at least one comma, or it errors out. Try this:

set lastname = left(lastname, charindex(',', lastname + ',') - 1)|||Thanks that did actually work.. not sure how that charindex worked. i was using to REPLACE statements to make it work. It was more efficient using your method.|||If you need a method of parsing name strings into component parts, I have a UDF that will do that too.