Update based on Select

I think that this is really easy, I just have never done it before.

Basically I have a two columned table: table1

It has the columns id, and name

talble1: (all have names)
-id
-name

Then I have

table2: (Some names are null)
-id
-name

I basically want to go through table2 and for any null names use the id to look up the name in table1 and then update table2 with this name.

Thanks

~Matthew