sachi=# select usesysid, usename, COALESCE(groname,'default') from pg_user u left join pg_group g on ','||array_to_string(grolist,',')||','   like '%,'||cast(usesysid as varchar(10))||',%' where usename='sachi' order by 2,1;

 usesysid | usename | coalesce 

----------+---------+----------

    16994 | sachi   | admin

(1 row)

sachi=#