Update and left outer join statements
Update t SET t.Column1=100FROM myTableA t LEFT JOIN myTableB t2 ON t2.ID=t.IDReplace myTableA with your table name and replace Column1 with your column name.
After this simply LEFT JOIN to tableB. t in this case is just an alias for myTableA. t2 is an alias for your joined table, in my example that is myTableB. If you don't like using t or t2 use any alias name you prefer - it doesn't matter - I just happen to like using those.
If what you need is UPDATE from SELECT statement you can do something like this:
UPDATE suppliers SET city = (SELECT customers.city FROM customersWHERE customers.customer_name = suppliers.supplier_name)
Just another example where the value of a column from table 1 is inserted into a column in table 2:
UPDATE AddressSET Phone1 = sp.PhoneFROM Address ad LEFT JOIN Speaker spON sp.AddressID = ad.IDWHERE sp.Phone <> ''