[mgsouth]

SELECT x, random() FROM foo ORDER BY x;

SELECT foo.x, bar.y FROM foo WHERE bar.z > random() ORDER BY foo.x;

SELECT x FROM foo ORDER BY x; -- Meanwhile, concurrent updates are happening to foo, so re-running the query gets a different result set.

"We choose to do this thing and the others, not because they are easy, but because we ask 'how hard can it be?'"