MySQL 8.0

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CREATE TABLE x SELECT 'aaa' a, 999 b UNION ALL SELECT 'bbb', 888 UNION ALL SELECT 'ccc', 777;
select * from x;

a
b

aaa
999

bbb
888

ccc
777

select * from x order by a<b;
select * from x order by a=b;
select * from x order by a<>b;
select * from x order by a<>b,b;

a
b

aaa
999

bbb
888

ccc
777

a
b

aaa
999

bbb
888

ccc
777

a
b

aaa
999

bbb
888

ccc
777

a
b

ccc
777

bbb
888

aaa
999