MySQL aliaslar

MySQL taxalluslari

Taxallus AS kalit so‘zi bilan yaratiladi va ko‘pincha ustun nomini o‘qish uchun qulay qilish uchun ishlatiladi.

Taxallus faqat so‘rov davomida mavjud.

Ustun sintaksisi uchun taxallus

SELECT column_name AS alias_name
FROM table_name;

Jadval sintaksisi uchun taxallus

SELECT column_name(s)
FROM table_name AS alias_name;

Demo ma’lumotlar bazasi

Quyida Northwind namunasidagi "Mijozlar" jadvalidan tanlov mavjud ma’lumotlar bazasi:

Mijoz ID	Mijoz nomi	Kontakt nomi	Manzil	Shahar	Pochta kodi	Mamlakat
1	Alfreds Futterkiste	Mariya Anders	Obere ko‘chasi. 57	Berlin	12209	Germaniya
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Konstitutsiya 2222	Meksika D.F.	05021	Meksika
3	Antonio Moreno Taqueria	Antonio Moreno	Mataderos 2312	Meksika D.F.	05023	Meksika
4	Shox atrofida	Tomas Xardi	120 Gannover kv.	London	WA1 1DP	UK
5	Berglunds snabbköp	Kristina Berglund	Berguvsvägen 8	Luleå	S-958 22	Shvetsiya

Ustunlar uchun taxallus

Quyidagi SQL ikkita taxallus yaratadi, biri CustomerID ustuni va biri CustomerName ustuni uchun:

Misol

SELECT CustomerID AS ID, CustomerName AS Customer
FROM Customers;

O‘zingiz sinab ko‘ring »

Bo‘shliqlar bilan taxallus

Agar taxallusingizda bir yoki bir nechta bo‘sh joy bo‘lishini istasangiz, masalan, “Aloqa qiluvchi shaxs” taxallus nomini bitta yoki qo‘sh tirnoq bilan o‘rab oling:

Misol

SELECT CustomerName AS Customer, ContactName AS "Contact Person"
FROM Customers;

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Ustunlarni birlashtirish

Quyidagi SQL to‘rtta ustunni (manzil, pochta indeksi, shahar va mamlakat) birlashtirgan "Manzil" nomli taxallusni yaratadi:

Misol

SELECT CustomerName, CONCAT_WS(', ', Address, PostalCode, City, Country) AS Address
FROM Customers;

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Jadvallar uchun taxallus

Quyidagi SQL CustomerID=4 (Around the Horn) bo‘lgan mijozning barcha buyurtmalarini tanlaydi. Biz "Customers" va "Orders" jadvallaridan foydalanamiz va ularga mos ravishda "c" va "o" taxalluslarini (alias) beramiz (bu yerda SQL’ni qisqaroq qilish uchun taxalluslardan foydalanamiz):

Misol

SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName='Around the Horn' AND c.CustomerID=o.CustomerID;

O‘zingiz sinab ko‘ring »

Quyidagi SQL yuqoridagi bilan bir xil, ammo taxalluslarsiz:

Misol

SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName
FROM Customers, Orders
WHERE Customers.CustomerName='Around the Horn' AND Customers.CustomerID=Orders.CustomerID;

O‘zingiz sinab ko‘ring »

Taxalluslar quyidagi hollarda foydalidir:

So‘rovda bir nechta jadval mavjud
So‘rovda funksiyalar qo‘llaniladi
Ustun nomlari uzun yoki unchalik o‘qilmaydi
Ikki yoki undan ortiq ustunlar birlashtiriladi

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