and { only { filter_eq { all_rows ; height ft ( m ) ; 504 } } ; eq { hop { filter_eq { all_rows ; height ft ( m ) ; 504 } ; name } ; one indiana square } } = true
select the rows whose height ft  m  record is equal to 504 . there is only one such row in the table . the name record of this unqiue row is one indiana square .