and { only { filter_not_eq { all_rows ; percentage of votes ; 100 % } } ; eq { hop { filter_not_eq { all_rows ; percentage of votes ; 100 % } ; election date } ; 1981 } } = true
select the rows whose percentage of votes record does not match to 100  . there is only one such row in the table . the election date record of this unqiue row is 1981 .