SQL: Conditional Insert/Update

Hi I am working with a table like the one below in SAP HANA:

Outcome  Value  Rating
Yes       0      null
Yes       20     null
No       -16     null

I need to populate the Rating column conditionally so that if:

Value > 15; Rating = 'High"
-15 <= Value <= 15; Rating = 'Medium" 
Value < -15; Rating = 'Low"

Is there anyway I can do this using an INSERT or UPDATE statement?