Kecualikan elemen array yang cocok

Sepertinya XOR antar array:

WITH set1 AS
(
 SELECT * FROM unnest('{1, 2, 5, 15}'::int[])
), set2 AS
(
 SELECT * FROM unnest('{1, 2, 3, 6, 7, 9, 15}'::int[])
), xor AS
(
  (SELECT * FROM set1
   UNION 
   SELECT * FROM set2)
  EXCEPT
  (SELECT * FROM set1
   INTERSECT 
   SELECT * FROM set2)
)
SELECT array_agg(unnest ORDER BY unnest)
FROM xor

Keluaran:

"{3,5,6,7,9}"

Cara kerjanya:

1. Hapus sarang kedua array
2. Hitung SUM
3. Hitung INTERSECT
4. Dari SUM - INTERSECT
5. Gabungkan ke larik

Atau Anda dapat menggunakan jumlah dari kedua operasi minus (kecuali):

(A+B) - (A^B)
<=>
(A-B) + (B-A)

Memanfaatkan FULL JOIN :

WITH set1 AS
(
 SELECT *
FROM unnest('{1, 2, 5, 15}'::int[])
), set2 AS
(
 SELECT *
 FROM unnest('{1, 2, 3, 6, 7, 9, 15}'::int[])
)
SELECT array_agg(COALESCE(s1.unnest, s2.unnest) 
                 ORDER BY COALESCE(s1.unnest, s2.unnest))
FROM set1 s1
FULL JOIN set2 s2
  ON s1.unnest = s2.unnest
WHERE s1.unnest IS NULL
  OR s2.unnest IS NULL;

EDIT:

Jika Anda hanya menginginkan elemen dari array kedua yang bukan yang pertama gunakan EXCEPT sederhana :

SELECT array_agg(unnest ORDER BY unnest)
FROM (SELECT * FROM unnest('{1, 2, 3, 6, 7, 9, 15}'::int[])
      EXCEPT
      SELECT * FROM unnest('{1, 2, 5, 15}'::int[])) AS sub

Keluaran:

"{3,6,7,9}"