SQL SELF JOIN
SQL Self JOIN (O‘z-o‘zini birlashtirish)
Self JOIN — bu oddiy join bo‘lib, bunda jadval o‘z-o‘ziga bog‘lanadi.
Self Join sintaksisi
SELECT column_name(s)
FROM table1 T1, table1 T2
WHERE condition;
T1 va T2 bir xil jadval uchun turli xil jadval taxalluslaridir.
Demo ma’lumotlar bazasi
Quyida tanlanma "Customers" jadvali 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 |
SQL Self Join misoli
quyidagi SQL operatori (so‘rovi) bir shahardan bo‘lgan mijozlarga mos keladi:
Misol
SELECT A.CustomerName AS CustomerName1, B.CustomerName AS CustomerName2,
A.City
FROM Customers A, Customers B
WHERE A.CustomerID <> B.CustomerID
AND A.City = B.City
ORDER BY A.City;
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