176. A da bor, B da yo'q

Reja (planned) va haqiqiy sotuv (actual) jadvallari bor. Kalit

ikkita ustundan iborat: (region, product).

Rejada bor, lekin haqiqatda umuman sotilmagan juftliklarni toping.

Ikki yo'l bilan yozish mumkin:

SELECT region, product FROM planned
EXCEPT
SELECT region, product FROM actual

yoki LEFT JOIN ... IS NULL bilan — lekin bunda ikkala ustunni ham

bog'lash kerak, faqat bittasini bog'lasangiz javob noto'g'ri chiqadi.

Rejada bir juftlik ikki marta yozilgan bo'lsa ham, natijada bir marta

chiqsin.

Ustunlar: region, product.

Saralash: region alifbo, keyin product alifbo.

planned: id INT PK, region VARCHAR, product VARCHAR

actual: id INT PK, region VARCHAR, product VARCHAR