How to modify update set from in Oracle

Someone in the group asked: how does table A (id,name) Table B (item_id,name,a_id) in Oracle now conform to a. Name=b. The ID of the a table of name is updated to a_id in table B

I say this: Update B set a_id=a.id from a inner join B on a.name=b.name

Then the elder brother executed, has been reported ORA-00933, later only know that Oracle does not have update set from this syntax, but can be flexible implementation

Update b Set b.a_id= (select a.ID from a where a.name=b.name);

How to modify update set from in Oracle