eq { diff { hop { filter_eq { all_rows ; theme ; great blue heron } ; issue price } ; hop { filter_eq { all_rows ; theme ; common eider } ; issue price } } ; 2 } = true
select the rows whose theme record fuzzily matches to great blue heron . take the issue price record of this row . select the rows whose theme record fuzzily matches to common eider . take the issue price record of this row . the first record is 2 larger than the second record .