<select>select person_id,fname,lname from normalised_personalia p join normalised_first_names f using(fid) join normalised_last_names l using(lid);</select>
<insert>
INSERT INTO denormalised_personalia(person_id,fname,lname)
values(?::integer,?::text,?::text)
ON CONFLICT (person_id) DO UPDATE
SET
fname = EXCLUDED.fname,
lname = EXCLUDED.lname
WHERE
denormalised_personalia.fname is distinct from EXCLUDED.fname
OR denormalised_personalia.lname is distinct from EXCLUDED.lname