buena como puedo solucionar este error Error Code: 1140. In aggregated query without GROUP BY, expression #1 of SELECT list contains nona...

buena como puedo solucionar este error

Error Code: 1140. In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ‘prueba_library.a.nationality’; this is incompatible with sql_mode=only_full_group_by

este error me sala cuando ejecuto el siguiente query

select nationality, count(book_id),

sum(if(year <1950, 1, 0)) as ‘<1950’,

sum(if(year >=1950 and year <1990,1,0)) as ‘<1990’,

sum(if(year >=1990 and year <2001,1,0 )) as ‘<2001’,

sum(if(year >=2001,1,0)) as '<hoy’

from books as b

join authors as a

on a.author_id = b.author_id

where a.nationality is not null;