oracle - beginner sql question pt.2 error ora-00933 SQL command not properly ended -

i have update tables assignment in dbms. can't figure out why error.

  update customers   set creditlimit = creditlimit * 1.25       from(select *            orders            amount > 250            having count(*) >= 2); 

any ideas?

the update statement doesn't have from clause, specified.
trying this: increase credit limit 25% customers have @ least 2 orders more 250 money.

update customers    set creditlimit = creditlimit * 1.25  (select count(*)           orders          amount > 250            , orders.customer_id = customers.customer_id)) >= 2; 

edit
noticed using oracle (the ora message). since potentially updating customers, believe performant way use "updatable join", or merge statement below:

merge   customers using (select customer_id          orders o         amount > 250         group             customer_id        having count(*) >= 2       ) orders     on(customers.customer_id = orders.customer_id) when matched    update       set customers.creditlimit = customers.creditlimit * 1.25;