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CREATE TABLE a ( id int, email text ); CREATE TABLE b ( id int, email text ); INSERT INTO a VALUES (1, 'a'), (1, 'b'), (2, 'c'), (5, 'e'); INSERT INTO b VALUES (3, 'a'), (3, 'd'), (4, 'e'), (4, 'f'), (3, 'b');
4 rows affected
5 rows affected
WITH combined AS ( SELECT a.email as a_email, b.email as b_email, array_remove(ARRAY[a.id, b.id], NULL) as ids FROM a FULL OUTER JOIN b ON (a.email = b.email) ), clustered AS ( SELECT DISTINCT ids FROM ( SELECT DISTINCT ON (unnest_ids) *, unnest(ids) as unnest_ids FROM combined ORDER BY unnest_ids, array_length(ids, 1) DESC ) s ) SELECT DISTINCT new_id, unnest(array_cat) as email FROM ( SELECT array_cat( array_agg(a_email) FILTER (WHERE a_email IS NOT NULL), array_agg(b_email) FILTER (WHERE b_email IS NOT NULL) ), row_number() OVER () as new_id FROM combined co JOIN clustered cl ON co.ids <@ cl.ids GROUP BY cl.ids ) s
new_id
email
1
c
2
a
2
b
2
d
3
e
3
f