MySQL 8.0

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create table test (txt varchar(32) );
insert into test values
('word word #12 '),
('word word \r\n word #333'),
('word word word');
select *
from test


txt


word word #12

word word 
 word #333

word word word


select *
from test
where txt rlike '.*#[[:digit:]]+[[:blank:]]*$';


txt


word word #12

word word 
 word #333