and { only { filter_eq { all_rows ; event ; 50 km } } ; and { eq { hop { filter_eq { all_rows ; event ; 50 km } ; year } ; 2011 } ; eq { hop { filter_eq { all_rows ; event ; 50 km } ; competition } ; world championships } } } = true
select the rows whose event record fuzzily matches to 50 km . there is only one such row in the table . the year record of this unqiue row is 2011 . the competition record of this unqiue row is world championships .