SQL 显示匹配 WHERE 语句的字段，否则显示其他字段

Question

这些是我正在使用的参数，我可以让条目显示与“礼服衬衫”项目匹配的条目，但如果它们与“礼服衬衫”不匹配，我不知道如何显示其他条目.我一直在尝试使用 AND/OR，但无法正确显示。

“显示所有订购过名为“Dress Shirt”的商品的客户的姓氏、名字、电话和总金额。还显示所有其他客户的姓氏、名字和电话。显示按姓氏排序的结果升序，然后是降序的 FirstName。"

SELECT LastName, FirstName, Phone, TotalAmount
FROM Customer, Invoice, Invoice_Item
WHERE Customer.CustomerID = Invoice.CustomerNumber AND Invoice.InvoiceNumber = 
Invoice_Item.InvoiceNumber AND Item ='Dress Shirt';

Answer 1

试试这个：

SELECT LastName, FirstName, Phone, TotalAmount
FROM Customer
INNER JOIN Invoice ON Customer.CustomerID = Invoice.CustomerNumber
LEFT JOIN Invoice_Item ON Invoice.InvoiceNumber = Invoice_Item.InvoiceNumber 
                      AND invoice_item.Item ='Dress Shirt'
;

Access 可能会坚持为联接使用括号，如下所示：

SELECT LastName, FirstName, Phone, TotalAmount
FROM ((Customer
INNER JOIN Invoice ON Customer.CustomerID = Invoice.CustomerNumber)
LEFT JOIN Invoice_Item ON Invoice.InvoiceNumber = Invoice_Item.InvoiceNumber 
                      AND invoice_item.Item ='Dress Shirt')
;

如果您不熟悉左连接，那么 this example 可能会有所帮助。

Answer 2

SELECT Lastname, FirstName, Phonem TotalAmount
FROM (Customer INNER JOIN Invoice ON Customer.CustomerID=Invoice.CustomerNumber) `LEFT JOIN Invoice_Item ON Invoice.InvoiceNumber=Invoice_item.InvoiceNumber
Where Invoice_item.Item='Dress Shirt'
Order by LastName, FirstName DESC;