Sorgu işleme sırası

Oracle SQL'ye Giriş

Hadrien Lacroix

Content Developer

İşleme sırası neden önemlidir?

Sorgularınızı optimize edin
- İstenmeyen sonuç yok
- Daha hızlı çalıştırma

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
    WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
    HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
->  FROM Invoice
    WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
    HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
->  WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
    HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
    WHERE BillingCity <> 'Paris' 
->  GROUP BY BillingCountry
    HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
    WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
->  HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

->  SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
    WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
    HAVING AVG(Total) > 100
    ORDER BY Average DESC

Örnek

    SELECT BillingCountry, AVG(Total) > 100) AS Average
    FROM Invoice
    WHERE BillingCity <> 'Paris' 
    GROUP BY BillingCountry
    HAVING AVG(Total) > 100
->  ORDER BY Average DESC

Ne ters gidebilir?

SELECT BillingCountry, 
       AVG(Total) > 100) AS Average
FROM Invoice
WHERE BillingCity <> 'Paris' 
GROUP BY BillingCountry
HAVING AVG(Total) > 100
ORDER BY Average DESC

WHERE, GROUP BY ve HAVING içinde takma adlar kullanılamaz
ORDER BY içinde takma adlar kullanılabilir

Ne ters gidebilir?

SELECT BillingCountry, 
       AVG(Total) > 100) AS Average
FROM Invoice
WHERE BillingCity <> 'Paris' 
GROUP BY BillingCountry
HAVING AVG(Total) > 100
ORDER BY Average DESC

Toplam değerler WHERE koşulunda filtrelenemez
Toplam değerler HAVING koşulunda filtrelenebilir

Ne ters gidebilir?

SELECT BillingCountry, 
       AVG(Total) > 100) AS Average
FROM Invoice
WHERE BillingCity <> 'Paris' 
GROUP BY BillingCountry
HAVING AVG(Total) > 100)
ORDER BY Average DESC

Tekil satırlar HAVING koşulunda filtrelenemez
Tekil satırlar WHERE koşulunda filtrelenebilir

Sorgu yürütme sırası

FROM ve JOINler: hangi verinin sorgulanacağını belirler
WHERE: tekil satırları filtreler
GROUP BY: satırları grupla
HAVING: grupları filtrele
SELECT: sütunları seç ve sütun işlevleri uygula
DISTINCT: yinelenenleri kaldır
UNION, UNION ALL, INTERSECT, MINUS: küme işleçleri uygula
ORDER BY: satırları sırala

Hadi pratik yapalım!

Oracle SQL'ye Giriş