MySQL EXISTS

MySQL EXISTS operatori

EXISTS operatori WHERE bandida quyi so‘rov biror qator qaytarishini tekshirish uchun ishlatiladi.

EXISTS operatori agar quyi so‘rov kamida bitta qatorni qaytarsa, TRUE, aks holda FALSE deb baholaydi.

EXISTS sintaksisi

SELECT column_name(s)
FROM table_name
WHERE EXISTS (subquery);

Demo ma’lumotlar bazasi

Quyida Northwind namunaviy ma’lumotlar bazasidagi “Mahsulotlar” jadvalidan tanlab olingan:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18.00
2	Chang	1	1	24 - 12 oz bottles	19.00
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10.00
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	22.00
5	Chef Anton's Gumbo Mix	2	2	36 boxes	21.35

Va "Yetkazib beruvchilar" jadvalidan tanlov:

SupplierID	Ta’minotchi nomi	Kontakt nomi	Manzil	Shahar	Pochta kodi	Mamlakat
1	Ekzotik suyuqlik	Sharlotta Kuper	49 Gilbert St.	London	EC1 4SD	UK
2	Yangi Orlean Kajun lazzatlari	Shelley Burke	P.O. 78934 quti	Yangi Orlean	70117	AQSh
3	Kelli buvining uyi	Regina Merfi	707 Oksford ko‘chasi.	Enn Arbor	48104	AQSh
4	Tokio savdogarlari	Yoshi Nagase	9-8 Sekimai Musashino-shi	Tokio	100	Yaponiya

MySQL EXISTS misollar

Quyidagi SQL har qanday yetkazib beruvchida 20 dan past narxga ega mahsulot borligini tekshiradi. Agar quyi so‘rov TRUE deb baholansa; Mahsulot narxi 20 dan past bo‘lgan yetkazib beruvchilarni sanab o‘ting:

Misol

SELECT SupplierName FROM Suppliers
WHERE EXISTS (
SELECT ProductName
FROM Products
WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20
);

O‘zingiz sinab ko‘ring »

Quyidagi SQL har qanday yetkazib beruvchida 22 ga teng narxga ega mahsulot mavjudligini tekshiradi. Agar quyi so‘rov TRUE deb baholansa; Mahsulot narxi 22 ga teng bo‘lgan yetkazib beruvchilarni sanab o‘ting:

Misol

SELECT SupplierName FROM Suppliers
WHERE EXISTS (
SELECT ProductName
FROM Products
WHERE Products.SupplierID = Suppliers.supplierID AND Price = 22
);

O‘zingiz sinab ko‘ring »

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