SQL:Membandingkan dua hitungan dari Tabel yang berbeda

Mulailah dengan mendapatkan jumlah untuk masing-masing individu:

# Sum of lakes
SELECT code, count(*) AS sum FROM lakes GROUP BY code

# Sum of mountains
SELECT code, count(*) AS sum FROM mountains GROUP BY code

Kemudian gabungkan hasilnya dan pilih semua baris di mana jumlah gunung untuk suatu negara kurang dari jumlah danau:

SELECT l.code AS code, l.sum AS lake_count, m.sum AS mountain_count
FROM
(SELECT code, count(*) AS sum FROM lakes GROUP BY code) AS l JOIN
(SELECT code, count(*) AS sum FROM mountains GROUP BY code) AS m
ON l.code = m.code
WHERE m.sum < l.sum