Help On Updating A Field In A Table With The Field Content Of Another Table

HI everybody need help on this..

I have two tables below

table1

country countryid

africa ___
usa ___
italy ___
Spain ___

table2

countryid country name

1 africa
2 germany
3 italy
4 usa


I need to write the countryid of table 2 to the field countryid in table1 using the criteria of the correspoinding country name table 2 to country of table 1 if it write countryid else 0..

THE RESULT WOULD BE

country countryid

africa 1
usa 4
italy 3
spain 0

thanks