using update query with subquery in Oracle sql
I would recommend to have a look into the merge into statement when youre deailing with oracle.

if you just want to update rows omit when not matched part of the statement

see http://www.oracle.com/webfolder/technetwork/de/community/apex/tipps/sql-merge/index.html and https://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_9016.htm