UNION Operator

SQL UNION Operator

UNION operatori ikkita yoki undan ortiq SELECT bayonotlarining natija to'plamini birlashtirish uchun ishlatiladi.

• Har bir SELECT bayonoti ichida UNION bir xil ustunlar soniga ega bo'lishi kerak.
• Ustunlar shuningdek, o'xshash ma'lumot turlariga ega bo'lishi kerak.
• Har bir SELECT bayonotidagi ustunlar ham bir xil tartibda bo'lishi kerak.

UNION Sintaksisi

SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;

UNION ALL Sintaksisi

UNION operatori faqat noyob qiymatlarni tanlaydi. Takroriy qiymatlarga ruxsat berish uchun, UNION ALL dan foydalaning:

SELECT column_name(s) FROM table1
UNION ALL
SELECT column_name(s) FROM table2;

Demo Ma'lumotlar Bazasi

Ushbu o'quv qo'llanmada biz mashhur Northwind namunaviy ma'lumotlar bazasidan foydalanamiz.

Quyida "Customers" jadvalidan bir tanlov:

Va "Suppliers" jadvalidan bir tanlov:

SQL UNION Misoli

Quyidagi SQL bayonoti "Customers" va "Suppliers" jadvalidan shaharlarni (faqat noyob qiymatlar) qaytaradi:

SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;

Eslatma: Agar ba'zi mijozlar yoki ta'minotchilar bir xil shaharni bo'lsa, har bir shahar faqat bir marta ro'yxatga olinadi, chunki UNION faqat noyob qiymatlarni tanlaydi. Takroriy qiymatlarni tanlash uchun UNION ALL dan foydalaning!

SQL UNION ALL Misoli

Quyidagi SQL bayonoti "Customers" va "Suppliers" jadvalidan shaharlarni (takroriy qiymatlar ham) qaytaradi:

SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;

SQL UNION WHERE Bilan

Quyidagi SQL bayonoti "Customers" va "Suppliers" jadvalidan nemis shaharlarini (faqat noyob qiymatlar) qaytaradi:

SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;

SQL UNION ALL WHERE Bilan

Quyidagi SQL bayonoti "Customers" va "Suppliers" jadvalidan nemis shaharlarini (takroriy qiymatlar ham) qaytaradi:

SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION ALL
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;

Boshqa UNION Misoli

Quyidagi SQL bayonoti barcha mijozlar va ta'minotchilarni ro'yxatga oladi:

SELECT 'Customer' AS Type, ContactName, City, Country
FROM Customers
UNION
SELECT 'Supplier', ContactName, City, Country
FROM Suppliers;