blocks|key|836533|text|第一个问题是您正在进行两个表之间的交叉联接。第二个问题是in中的子查询没有返回任何结果。‘'Dress’可能不是一个有效的值。但是，考虑一个更类似的查询：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|836534|SELECT+distinct+FirstName,+LastName
FROM+HW2G_CUSTOMER+c+join
+++++HW2G_ORDER_ITEM+i
+++++on+c.customerID+=+i.customerID
WHERE+i.Item+=+‘Dress+Shirt’
ORDER+BY+LastName+ASC,+FirstName+DESC;|code-block|syntax|javascript|836535|这不会解决这个问题(它是字符串"Dress“)，但它是向前移动的更好的语法。|836536|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The first problem is that you are doing a cross join between two tables. The second is that the subquery in the IN is not returning any results. 'Dress Shirt" is probably not a valid value. But, consider a query more like:

<pre><code>SELECT distinct FirstName, LastName
FROM HW2G_CUSTOMER c join
 HW2G_ORDER_ITEM i
 on c.customerID = i.customerID
WHERE i.Item = ‘Dress Shirt’
ORDER BY LastName ASC, FirstName DESC;
</code></pre>

This won't fix the problem (which is the string "Dress Shirt"), but it is better syntax for moving forward.

blocks|key|4613818|text|你肯定不想要你现在拥有的东西，因为你正在做一个交叉连接。看看这把小提琴：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4613819|http://www.sqlfiddle.com/#!3/30abb/5|offset|length|4613820|SELECT+FirstName,+LastName
FROM+HW2G_CUSTOMER+WHERE+CustomerId+IN
++++(SELECT+CustomerId
+++++FROM+HW2G_ORDER_ITEM
+++++WHERE+Item+=+'Dress+Shirt')
ORDER+BY+LastName+ASC,+FirstName+DESC;|code-block|syntax|javascript|4613821|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|10|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|H|7|W|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|C]]]]

You definitely don't want what you have right now, because you're doing a cross join. Take a look at this fiddle:

<a href="http://www.sqlfiddle.com/#!3/30abb/5" rel="nofollow">http://www.sqlfiddle.com/#!3/30abb/5</a>

<pre><code>SELECT FirstName, LastName
FROM HW2G_CUSTOMER WHERE CustomerId IN
 (SELECT CustomerId
 FROM HW2G_ORDER_ITEM
 WHERE Item = 'Dress Shirt')
ORDER BY LastName ASC, FirstName DESC;
</code></pre>

blocks|key|4559009|text|--+maybe+a+bit+cleaner+than+@aqinas+'s+solution?
WITH+wanted+AS+(
++SELECT+DISTINCT+CustomerId
+++++FROM+HW2G_ORDER_ITEM
+++++WHERE+Item+=+'Dress+Shirt'
+++)
SELECT+FirstName,+LastName
FROM+HW2G_CUSTOMER+cus
JOIN+wanted+wa+ON+wa.CustomerId+=+cus.CustomerId
ORDER+BY+LastName+ASC,+FirstName+DESC
+;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4559010|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>-- maybe a bit cleaner than @aqinas 's solution?
WITH wanted AS (
 SELECT DISTINCT CustomerId
 FROM HW2G_ORDER_ITEM
 WHERE Item = 'Dress Shirt'
 )
SELECT FirstName, LastName
FROM HW2G_CUSTOMER cus
JOIN wanted wa ON wa.CustomerId = cus.CustomerId
ORDER BY LastName ASC, FirstName DESC
 ;
</code></pre>

I'm attempting to get a subquery in addition to a join statement that would display the FirstName and LastName of all customers who have had an order with an Item named 'Dress Shirt'. Then I have to report the results sorted by LastName in ascending order and then FirstName in descending order. This is what I have, but it keeps giving me 'NO ROWS SELECTED':

<pre><code>SELECT FirstName, LastName
FROM HW2G_CUSTOMER, HW2G_ORDER_ITEM
WHERE Item IN 
 (SELECT Item
 FROM HW2G_ORDER_ITEM
 WHERE Item = ‘DressShirt’)
ORDER BY LastName ASC, FirstName DESC;
</code></pre>

What am I doing wrong?

Subquery - Join

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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除了一个join语句之外，我还试图获得一个子查询，该语句将显示所有已经订购了名为“连衣裙”的产品的客户的FirstName和LastName。然后，我必须先按LastName的升序排序，然后按FirstName的降序排序。这就是我所拥有的，但它总是给我“没有选择行”：SELECT FirstName, LastName...

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