Change all of a field in table, very simple I ma not aSQL guy

Hi,
This will be super easy I am sure. SQL is not my normal field and I have not been able to get this quite right, also I am scared to mess up!

I have a table wp_postmeta
It has 4 columns meta_id / post_id / meta_key / meta_value
meta_key has many values, one is _backorders
this can have 3 different meta_values yes / no / notify

I want to set all of the _backorder meta_value’s to = no

What would the query be
Thanks

UPDATE wp_postmeta
   SET meta_value = 'no'
 WHERE meta_key = '_backorders'