An even simpler demonstration that omits the subquery in the FROM clause:

<blockquote><pre>
CREATE TABLE t1(id1, value1);
INSERT INTO t1 VALUES(4469,2),(4469,1);
CREATE TABLE t2 (value2);
INSERT INTO t2 VALUES(1);
SELECT (SELECT sum(value2=value1) FROM t2), max(value1)
  FROM t1
 GROUP BY id1;