blocks|key|4704714|text|将日期字段添加到您的选择中，并按其分组。否则，mysql扩展无法识别您想要按日期分组，并将所有结果聚合到一列中。因为你得到的是0计数，你的where子句肯定不工作了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4704715|您的日期格式似乎不正确。通常是YYYY/MM/DD格式(标准格式)；或者使用SELECT+STR_TO_DATE('17/09/2010','%25d/%25m/%25Y');指定格式|offset|length|style|CODE|4704716|MySQL+retrieves+and+displays+DATE+values+in+'YYYY-MM-DD'+format.+The+supported+range+is+'1000-01-01'+to+'9999-12-31'.|4704717|下面使用隐式转换和默认日期格式将字符串日期转换为有效日期。|4704718|SELECT+inicio_normal,+count(*)+
FROM+`castigos`+
WHERE+inicio_normal='2017/05/06'+
++AND+cod_emplazamiento=1+
GROUP+BY+inicio_normal|code-block|syntax|javascript|4704719|否则，就是在做数学运算，并将该日期与为该日期存储的数字进行比较。|4704720|了解日期应该存储在date数据类型中，当您查询日期时，您将传入一个字符串，该字符串将转换为date数据类型进行比较。因此，您需要使用标准格式，或者将字符串转换为日期，以便数据库引擎知道如何将您的格式转换为日期。|4704721|entityMap|0|LINK|mutability|MUTABLE|url|https://dev.mysql.com/doc/refman/5.7/en/datetime.html^0|0|12|18|0|0|39|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@$D|17|E|18|1|19]]|A|$]]|$1|J|3|K|5|6|7|1A|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|1B|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1C|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1D|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

Add the date field to your select and group by it. Otherwise mysql extensions doesn't recognize you want to group by the date and will aggregrate all the results into 1 column. And since you are getting 0 count, you're where clause must not be working.

Your date format seems malformed. usually YYYY/MM/DD format (standard format); 
or specify a format using <code>SELECT STR_TO_DATE('17/09/2010','%d/%m/%Y');</code>

<a href="https://dev.mysql.com/doc/refman/5.7/en/datetime.html" rel="nofollow noreferrer">MySQL retrieves and displays DATE values in 'YYYY-MM-DD' format. The supported range is '1000-01-01' to '9999-12-31'.</a>

the below uses the implicit casting and default date format to convert the string date to a valid date.

<pre><code>SELECT inicio_normal, count(*) 
FROM `castigos` 
WHERE inicio_normal='2017/05/06' 
 AND cod_emplazamiento=1 
GROUP BY inicio_normal
</code></pre>

Otherwise its doing math and comparing that date to the number stored for the date.

Understand dates should be stored in a date datatype and when you query dates you're passing in a string that is being cast to a date datatype for comparison. So you need to use the standard format, or cast your string to a date so the db engine knows how to convert your format to a date.

blocks|key|1206912|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1206913|SELECT+count(*)+FROM+`castigos`+WHERE+inicio_normal="05/06/2017"+AND+cod_emplazamiento=1+GROUP+BY+inicio_normal|code-block|syntax|javascript|1206914|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 this :

<pre><code>SELECT count(*) FROM `castigos` WHERE inicio_normal="05/06/2017" AND cod_emplazamiento=1 GROUP BY inicio_normal
</code></pre>

blocks|key|1172038|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1172039|，其中inicio_normal=05/06/2017|blockquote|1172040|1172041|1172042|如果你将3除以6，那么到2017年，你会得到一个非常小的值。如果您使用reformat+this+as+a+date+(例如20170605，如果您给我们一个欧洲格式的日期-+dd/mm/yyyy)，那么您的查询将找到您向我们显示的行。|offset|length|1172043|entityMap|0|LINK|mutability|MUTABLE|url|https://dev.mysql.com/doc/refman/5.7/en/date-and-time-literals.html^0|0|0|0|0|Z|N|0|0^^$0|@$1|2|3|-4|4|5|6|R|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|S|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|T|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|U|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|V|7|@]|8|@$H|W|I|X|1|Y]]|9|$]]|$1|J|3|-4|4|5|6|Z|7|@]|8|@]|9|$]]]|K|$L|$4|M|N|O|9|$P|Q]]]]

<blockquote>
 WHERE inicio_normal=05/06/2017
</blockquote>

If you divide 3 by 6 then by 2017 you get a very small value indeed. OTOH if you <a href="https://dev.mysql.com/doc/refman/5.7/en/date-and-time-literals.html" rel="nofollow noreferrer">reformat this as a date</a> (e.g. 20170605, if you gave us a European formatted date - dd/mm/yyyy) then your query will find the rows you showed us.

i want to do a count of two columns in mysql. One of the columns is a string but another is a date like 06/08/2017 and when i do my query i get 0 results.

<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-html lang-html prettyprint-override"><code>SELECT count(*) FROM `castigos` WHERE inicio_normal=05/06/2017 AND cod_emplazamiento=1</code></pre>
</div>
</div>


I have entries of that data but its dont show me anything. Maybe the type of data in the date is wrong?

What should i do?
<a href="https://i.stack.imgur.com/u34z9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/u34z9.png" alt="enter image description here"></a>

How can i do a count of two columns in mysql?

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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我想在mysql中计算两列。其中一列是字符串，另一列是类似于06/08/2017的日期，当我执行查询时，我得到0个结果。​SELECT count(*) FROM `castigos` WHERE inicio_normal=05/06/2017 AND cod_emplazamiento=1​我有这些数据的条目，但它...

问如何在mysql中对两列进行计数？
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问如何在mysql中对两列进行计数？EN