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使用Chinook Test Database我寫這個SQL語句來顯示有兩個特定客戶訂購的所有曲目:如何使用SQL查找雙打?
SELECT inv.BillingCity,cus.LastName,tra.Name
FROM invoice AS inv
JOIN customer AS cus ON inv.CustomerId=cus.CustomerId
JOIN invoiceline inl ON inv.InvoiceId=inl.InvoiceId
JOIN track tra ON tra.TrackId=inl.TrackId
WHERE cus.LastName IN ('Schneider','Schröder')
ORDER BY inv.BillingCity,cus.LastName,tra.Name
我看到有,是由一個客戶訂購兩次軌道:
我該如何編寫一條SQL語句來查找這樣的雙打,即「返回一個客戶多次訂購的所有曲目」?