blocks|key|2578472|text|我认为这是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2578473|SELECT+id+FROM+tagPairs+WHERE+tag1+XOR+tag2|code-block|syntax|javascript|2578474|仅检查其中一个字段是否为非NULL+(如果确实如此)。|2578475|澄清问题：|2578476|您是说值($tag1或$tag2)可以在任何一个字段(tag1或tag2)中吗？除了$tag1、$tag2、NULL之外，这两个字段还能有其他值吗？|2578477|如果这两个问题的答案都是肯定的，那么我同意你正在做一个基本的XOR。如果您不知道如何在这里使用XOR，那么逻辑上"a+xor+b“的等价物是|2578478|(+a+and+not+b+)+or+
(+b+and+not+a+)|2578479|在你的情况下|2578480|a+=+(tag1+in+($tag1,$tag2))
b+=+(tag2+in+($tag1,$tag2))

not+a+=+(tag1+not+in+($tag1,$tag2))
not+b+=+(tag2+not+in+($tag1,$tag2))|2578481|因此，只需替换，您就会得到：|2578482|(++(tag1+in+($tag1,$tag2))+and+(tag2+not+in+($tag1,$tag2))++)+or+
(++(tag2+in+($tag1,$tag2))+and+(tag1+not+in+($tag1,$tag2))++)|2578483|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

I think that this:

<pre><code>SELECT id FROM tagPairs WHERE tag1 XOR tag2
</code></pre>

only checks that one of the fields is not NULL if it even does that.

Clarification Question:

Are you saying that either value ($tag1 or $tag2) could be in either field (tag1 or tag2)?
Can either of the fields have other values besides $tag1, $tag2, NULL?

If the answer to both questions is yes then I agree that you are doing a basic XOR. If you can't figure out how to use XOR here, then the logical equivalent of "a xor b" is 

<pre><code>( a and not b ) or 
( b and not a )
</code></pre>

In your case 

<pre><code>a = (tag1 in ($tag1,$tag2))
b = (tag2 in ($tag1,$tag2))

not a = (tag1 not in ($tag1,$tag2))
not b = (tag2 not in ($tag1,$tag2))
</code></pre>

So then just substitute and you get:

<pre><code>( (tag1 in ($tag1,$tag2)) and (tag2 not in ($tag1,$tag2)) ) or 
( (tag2 in ($tag1,$tag2)) and (tag1 not in ($tag1,$tag2)) )
</code></pre>

blocks|key|103135|text|尝试使用XOR。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|103136|entityMap|0|LINK|mutability|MUTABLE|url|http://dev.mysql.com/doc/refman/5.0/en/logical-operators.html#operator_xor^0|4|3|4|3|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

Try using <a href="http://dev.mysql.com/doc/refman/5.0/en/logical-operators.html#operator_xor" rel="nofollow noreferrer"><code>XOR</code></a>.

blocks|key|1168298|text|我认为您的基本逻辑是好的，但是您需要更多的括号来将您的前两个IN子句组合在一起。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1168299|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I think your basic logic is good but you need more parenthesis to group your first two IN clauses together.

blocks|key|1168316|text|尝试编写2个查询，然后为输出编写“union+all”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1168317|1168318|查找tag1+=+$tag1+&+tag1+<>+$tag2+|ordered-list-item|1168319|查找tag2+=$tag2&+tag2+<>+$tag1|1168320|1168321|这只是逻辑表示，我以前从未使用过MySQL。|1168322|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|N|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|P|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|L|$]]

try writing 2 queries &amp; then 'union all' for output.

<ol>
<li>look for tag1 = $tag1 &amp; tag1 &lt;> $tag2</li>
<li>look for tag2 = $tag2 &amp; tag2 &lt;> $tag1</li>
</ol>

This is just logical representation, i have never used MySQL before.

blocks|key|2578404|text|尝试：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2578405|SELECT+id+FROM+tagPairs+WHERE+(tag1+=+'$tag1')+XOR+(tag2+=+'$tag2')|code-block|syntax|javascript|2578406|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try:

<pre><code>SELECT id FROM tagPairs WHERE (tag1 = '$tag1') XOR (tag2 = '$tag2')
</code></pre>

blocks|key|1168348|text|WHERE+tag1+IN+($tag1,+$tag2)
OR+tag2+IN+($tag1,+$tag2)
AND+NOT+(tag1+IN+($tag1,+$tag2)+AND+tag2+IN+($tag1,+$tag2))|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1168349|这纯粹是猜测，我从来没有用过MySQL。没有操作员吗？我希望有。|unstyled|1168350|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>WHERE tag1 IN ($tag1, $tag2)
OR tag2 IN ($tag1, $tag2)
AND NOT (tag1 IN ($tag1, $tag2) AND tag2 IN ($tag1, $tag2))
</code></pre>

This is pure speculation, I never used MySQL. Is there NOT operator? I hope there is.

blocks|key|103200|text|当心nulls。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|103201|WHERE+(tag1+IN+($tag1,+$tag2)
++++++OR+tag2+IN+($tag1,+$tag2))
++AND+(tag1+IS+NULL
++++++OR+tag2+IS+NULL
++++++OR+NOT(tag1+IN+($tag1,+$tag2)+AND+tag2+IN+($tag1,+$tag2)))|code-block|syntax|javascript|103202|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Beware of nulls.

<pre><code>WHERE (tag1 IN ($tag1, $tag2)
 OR tag2 IN ($tag1, $tag2))
 AND (tag1 IS NULL
 OR tag2 IS NULL
 OR NOT(tag1 IN ($tag1, $tag2) AND tag2 IN ($tag1, $tag2)))
</code></pre>

i need help with one more sql query.

if i've got 2 columns in a table:

<pre><code>tag1 tag2
</code></pre>

and want to select rows that got either $tag1 OR $tag2 but never $tag1 AND $tag2, how could i write the sql query?

i've tried with:

<pre><code> SELECT id
 FROM tagPairs
 WHERE (tag1 IN ($tag1, $tag2))
 OR (tag2 IN ($tag1, $tag2))
 AND ((tag1 != $tag1 OR tag1Id != $tag2) AND (tag2 != $tag1 OR tag2 != $tag2))
</code></pre>

but it doesnt seem to work.

would appreciate some help here, thanks!

help with a sql query

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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我还需要一个sql查询的帮助。如果我在一个表中有两列：tag1 tag2并且希望选择获得$tag1或$tag2但从未获得$tag1和$tag2的行，我该如何编写sql查询呢？我已经尝试过了：    SELECT id    FROM tagPairs    WHERE (tag1 IN ($tag1, $tag2))    OR (tag2 IN ($tag1, $tag2))    AND ((

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