SELECT DISTINCT buyrug'i
SELECT DISTINCT buyrug'idan, bir-biriga o'xshash bo'lmagan, ya'ni unikal qiymatlarni olish uchun foydalaniladi.Jadval, ustun ichida ko'pincha takroriy qiymatlar qamrab olingan bo'ladi; va ba'zida siz faqatgina o'xshash bo'lmagan qiymatlarni ro'yhatini olishni istashingiz mumkin.
SELECT DISTINCT sintaksis
SELECT DISTINCT ustun1, ustun2, ...
FROM jadval_nomi;
Quyida, "Murad Buildings" namuna uchun keltirilgan ma'lumot bazasidagi chet ellik "Xaridorlar" jadvalidan tanlanma ro'yhati keltirilgan:
CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
---|---|---|---|---|---|---|
1 |
Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
4 |
Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |
Yuqoridagi namunani DISTINCT-siz, SELECT orqali tanlab olamiz:
Quyidagi SQL buyruq "Xaridorlar" jadvalidagi "Country" ustunidan barcha qiymatlar(o'xshash qiymlarni ham)ni tanlab oladi:
SELECT Country FROM Customers;
Endi ushbu namunani, SELECT DISTINCT bilan ko'rsak:
SELECT DISTINCT Country FROM Customers;
Quyidagi SQL buyruqda, xaridorlarning bir-biriga o'xshash bo'lmagan holda davlatlar sonini chiqarib beradi:
SELECT COUNT(DISTINCT Country) FROM Customers;
Mavzular ro'yhati