update with inner join
#my thought is to try

```python
def test():
    with my_app.db.database.atomic():
        Customer.update(x=CustomerRep.select(CustomerRep.x)
                        .where(CustomerRep.acct == Customer.acct)
                        .order_by(CustomerRep.id.desc())
                        .limit(1)).execute()
        Customer.update(y=CustomerRep.select(CustomerRep.y)
                        .where(CustomerRep.acct == Customer.acct)
                        .order_by(CustomerRep.id.desc())
                        .limit(1)).execute()
```
 Did you happen to notice, when commenting or creating your issue that your code was not formatted? Please take the extra 10 seconds to do this when submitting issues. So, unfortunately, Peewee does not really support updates with joins. In fact, I don't know if any of the RDBMS's that Peewee supports allow that syntax.

* https://www.postgresql.org/docs/current/static/sql-update.html
* https://www.sqlite.org/lang_update.html

Check out this example for some ideas: http://docs.peewee-orm.com/en/latest/peewee/query_examples.html#update-a-row-based-on-the-contents-of-another-row
hello,

what is the syntax for a peewee query such as the following?  Is there a good way to figure this out on my own (like an sql to query syntax generator?).
```sql
update
    customer
 set
    customer.x = customerrep.x,
    customer.y = customerrep.y
from
    customer cust
inner join
    customerrep custrep
on 
    cust.acct = custrep.acct
```