select msgid from group1 where subj like '%hakusana%'
union
select msgid from group2 where subj like '%hakusana%'
union
[...]
select msgid from groupn-1 where subj like '%hakusana%'
union
select msgid from groupn where subj like '%hakusana%';


select msgid from group1, group2, [...], groupn-1, groupn where subj like '%hakusana%';

select msgid from (select name from groups where subs = 1) where subj like '%hakusana%';