Oracle 23c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
  create table cities 
   (objectid int, 
	population_centre varchar2(255), 
	population_2021 number(38,1), 
	other_columns varchar2(255)
   ) 
begin
insert into cities (objectid,population_centre,population_2021,other_columns) values (11,'Calgary',1305550,'a');
insert into cities (objectid,population_centre,population_2021,other_columns) values (23,'Edmonton',1151635,'b');
insert into cities (objectid,population_centre,population_2021,other_columns) values (31,'Halifax',348634,'c');
insert into cities (objectid,population_centre,population_2021,other_columns) values (32,'Hamilton',729560,'d');
insert into cities (objectid,population_centre,population_2021,other_columns) values (37,'Kelowna',181380,'e');
insert into cities (objectid,population_centre,population_2021,other_columns) values (40,'Kitchener',522888,'f');
insert into cities (objectid,population_centre,population_2021,other_columns) values (45,'London',423369,'g');
insert into cities (objectid,population_centre,population_2021,other_columns) values (51,'Montreal',3675219,'h');
insert into cities (objectid,population_centre,population_2021,other_columns) values (58,'Oshawa',335949,'i');
insert into cities (objectid,population_centre,population_2021,other_columns) values (59,'Ottawa–Gatineau',1068821,'j');
insert into cities (objectid,population_centre,population_2021,other_columns) values (65,'Quebec City',733156,'k');
insert into cities (objectid,population_centre,population_2021,other_columns) values (67,'Regina',224996,'l');
insert into cities (objectid,population_centre,population_2021,other_columns) values (76,'Saskatoon',264637,'m');
insert into cities (objectid,population_centre,population_2021,other_columns) values (82,'St. Catharines – Niagara Falls',242460,'n');
insert into cities (objectid,population_centre,population_2021,other_columns) values (83,'St. John''s',185565,'o');
insert into cities (objectid,population_centre,population_2021,other_columns) values (90,'Toronto',5647656,'p');
insert into cities (objectid,population_centre,population_2021,other_columns) values (92,'Vancouver',2426160,'q');
insert into cities (objectid,population_centre,population_2021,other_columns) values (94,'Victoria',363222,'r');
insert into cities (objectid,population_centre,population_2021,other_columns) values (98,'Windsor',306519,'s');
insert into cities (objectid,population_centre,population_2021,other_columns) values (99,'Winnipeg',758515,'t');
end;
/
1 rows affected

select *
from cities
where population_2021 = (select max(population_2021) from cities)
or population_2021 = (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities))
or population_2021 = (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities)))
or population_2021 = (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities where population_2021 < (select max(population_2021) from cities))))
order by population_2021


OBJECTID
POPULATION_CENTRE
POPULATION_2021
OTHER_COLUMNS


11
Calgary
1305550
a

92
Vancouver
2426160
q

51
Montreal
3675219
h

90
Toronto
5647656
p
OBJECTID	POPULATION_CENTRE	POPULATION_2021	OTHER_COLUMNS
11	Calgary	1305550	a
92	Vancouver	2426160	q
51	Montreal	3675219	h
90	Toronto	5647656	p