This SQL statement example is very close to what I think I need...

 update table1 set value1 = x.value1 from 
      (select value1, code from table2 
       where code = something)  as x 

However, what I need to do is change the "something" in the above example to a value from the row that is being updated.

For example, I tried this but it didn't work:

 update table1 A set value1 = x.value1 from 
      (select value1, code from table2 
       where code = A.something)  as x 

This is a one time operation to update an existing table and I'm not really looking for high performance way to do this. Any solution that gets the task done is good enough.