CREATE TABLE t1 (
  pk        integer PRIMARY KEY,
  name      text NOT NULL,
  somedata  integer
);

insert into t1 values ( 1, "kolya", 5 );
insert into t1 values ( 2, "petya", 3 );
insert into t1 values ( 3, "vasya", 4 );

CREATE TABLE t2 (
  pk        integer PRIMARY KEY,
  name      text NOT NULL,
  somedata  integer
);

insert into t2 values ( 1, "kolya", 555 );
insert into t2 values ( 2, "petya", 555 );
insert into t2 values ( 3, "vasya", 555 );

UPDATE t2 
SET t2.somedata = t1.somedata
WHERE t2.name = t1.name

UPDATE t1, t2 
SET  t2.somedata = t1.somedata
WHERE t2.name = t1.name

UPDATE t2 
SET t2.somedata = t1.somedata
from t1
WHERE t2.name = t1.name

update t2 set somedata=(select t1.somedata from t1 where t2.name=t1.name);