MySQL 8.0

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select version();


version()


8.0.23


create table emp 
(
  doj date,
  is_month_end bool as (doj = last_day(doj))
);
insert into emp (doj)
values 
  (date '2021-03-01'),
  (date '2021-04-30'),
  (date '2020-12-27'),
  (date '2020-10-31'),
  (date '2021-01-01'),
  (date '2021-02-28'),
  (date '2020-11-20');
create index idx_month_ends on emp (is_month_end);
delete from emp where not is_month_end;
select * from emp;


doj
is_month_end


2021-04-30
1

2020-10-31
1

2021-02-28
1