entityMap|blocks|key|dtca7|text|它在抱怨|type|unstyled|depth|inlineStyleRanges|entityRanges|data|9jb3e|COUNT(DISTINCT+dNum)+AS+ud|code-block|syntax|js|2u5tv|子查询内部。子查询只能返回一列，除非您正在执行exists查询。我不知道为什么你要对同一列做两次计数，表面上看，这对你正在做的事情来说是多余的。这里的子查询只是一个过滤器它与join不同。也就是说，您可以使用它来限制数据，而不是指定要返回的列。^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

It's complaining about 

<pre><code>COUNT(DISTINCT dNum) AS ud 
</code></pre>

inside the subquery. Only one column can be returned from the subquery unless you are performing an exists query. I'm not sure why you want to do a count on the same column twice, superficially it looks redundant to what you are doing. The subquery here is only a filter it is not the same as a join. i.e. you use it to restrict data, not to specify what columns to get back.

entityMap|blocks|key|8lmm3|text|您不能在子查询中返回两个(或多个)列来在WHERE+A_ID+IN+(subquery)子句-应该比较哪一列A_ID到？子查询必须仅返回与IN。因此，查询需要采用以下形式：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|9uis2|SELECT+*+From+ThisTable+WHERE+ThisColumn+IN+(SELECT+ThatColumn+FROM+ThatTable)|code-block|syntax|js|8dav4|您还希望添加排序，以便只从最顶端的行中进行选择，但不需要将计数作为列返回即可进行排序；ORDER子句独立于查询返回的列。|cr597|尝试如下所示：|eko8d|select+count(distinct+dNum)+
from+myDB.dbo.AQ+
where+A_ID+in
++++(SELECT+DISTINCT+TOP+(0.1)+PERCENT+A_ID
++++FROM+myDB.dbo.AQ+
++++WHERE+M+>+1+and+B+=+0
++++GROUP+BY+A_ID+
++++ORDER+BY+COUNT(DISTINCT+dNum)+DESC)|javascript^0|K|O|1I|4|1X|2|0|0|17|5|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|S|9|@$A|T|B|U|C|D]|$A|V|B|W|C|D]|$A|X|B|Y|C|D]]|E|@]|F|$]]|$2|G|4|H|6|I|8|Z|9|@]|E|@]|F|$J|K]]|$2|L|4|M|6|7|8|10|9|@$A|11|B|12|C|D]]|E|@]|F|$]]|$2|N|4|O|6|7|8|13|9|@]|E|@]|F|$]]|$2|P|4|Q|6|I|8|14|9|@]|E|@]|F|$J|R]]]]

You can't return two (or multiple) columns in your subquery to do the comparison in the <code>WHERE A_ID IN (subquery)</code> clause - which column is it supposed to compare <code>A_ID</code> to? Your subquery must only return the one column needed for the comparison to the column on the other side of the <code>IN</code>. So the query needs to be of the form:

<pre><code>SELECT * From ThisTable WHERE ThisColumn IN (SELECT ThatColumn FROM ThatTable)
</code></pre>

You also want to add sorting so you can select just from the top rows, but you don't need to return the COUNT as a column in order to do your sort; sorting in the <code>ORDER</code> clause is independent of the columns returned by the query. 

Try something like this:

<pre><code>select count(distinct dNum) 
from myDB.dbo.AQ 
where A_ID in
 (SELECT DISTINCT TOP (0.1) PERCENT A_ID
 FROM myDB.dbo.AQ 
 WHERE M &gt; 1 and B = 0
 GROUP BY A_ID 
 ORDER BY COUNT(DISTINCT dNum) DESC)
</code></pre>

entityMap|blocks|key|bin2u|text|在将返回值分配给变量的where查询中，应该只返回一列和一行。示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|algev|select+*+from+table1+where+Date+in+(select+*+from+Dates)+--+Wrong
select+*+from+table1+where+Date+in+(select+Column1,Column2+from+Dates)+--+Wrong
select+*+from+table1+where+Date+in+(select+Column1+from+Dates)+--+OK|code-block|syntax|javascript^0|0^^$0|$]|1|@$2|3|4|5|6|7|8|H|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|I|9|@]|A|@]|B|$F|G]]]]

You should return only one column and one row in the where query where you assign the returned value to a variable. Example:

<pre><code>select * from table1 where Date in (select * from Dates) -- Wrong
select * from table1 where Date in (select Column1,Column2 from Dates) -- Wrong
select * from table1 where Date in (select Column1 from Dates) -- OK
</code></pre>

entityMap|blocks|key|8c2eq|text|除了这里非常好的响应之外，如果你想原样使用子查询，你也可以尝试这样做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4iesg|方法：|offset|length|style|BOLD|dlc73|1)从子查询中选择所需的列(仅1)|31qsu|2)使用where映射列名|4p9ih|代码：|fafo1|SELECT+count(distinct+dNum)
+FROM+myDB.dbo.AQ
+WHERE+A_ID+in+
+++(
++++SELECT+A_ID+
++++FROM+(SELECT+DISTINCT+TOP+(0.1)+PERCENT+A_ID,+COUNT(DISTINCT+dNum)+AS+ud+
++++++++++FROM+++++++++myDB.dbo.AQ
++++++++++WHERE+++++M+>+1+and+B+=+0+
++++++++++GROUP+BY+A_ID+ORDER+BY+ud+DESC
+++++++++)+a+
+++)|code-block|syntax|javascript^0|0|0|3|0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|T|9|@]|A|@]|B|$]]|$2|C|4|D|6|7|8|U|9|@$E|V|F|W|G|H]]|A|@]|B|$]]|$2|I|4|J|6|7|8|X|9|@]|A|@]|B|$]]|$2|K|4|L|6|7|8|Y|9|@]|A|@]|B|$]]|$2|M|4|N|6|7|8|Z|9|@]|A|@]|B|$]]|$2|O|4|P|6|Q|8|10|9|@]|A|@]|B|$R|S]]]]

Apart from very good responses here, you could try this as well if you want to use your sub query as is.

Approach:

1) Select the desired column (Only 1) from your sub query

2) Use where to map the column name

Code:

<pre><code> SELECT count(distinct dNum)
 FROM myDB.dbo.AQ
 WHERE A_ID in 
 (
 SELECT A_ID 
 FROM (SELECT DISTINCT TOP (0.1) PERCENT A_ID, COUNT(DISTINCT dNum) AS ud 
 FROM myDB.dbo.AQ
 WHERE M &gt; 1 and B = 0 
 GROUP BY A_ID ORDER BY ud DESC
 ) a 
 )
</code></pre>

entityMap|blocks|key|33d4i|text|为了防止它对某些人有帮助，下面是导致我出现这个错误的原因:我需要一个过程来返回json，但我省略了for+json路径|type|unstyled|depth|inlineStyleRanges|entityRanges|data|19plg|set+@jsonout+=+(SELECT+ID,+SumLev,+Census_GEOID,+AreaName,+Worksite+
++++++++++++from+CS_GEO+G+(nolock)+
++++++++++++++++join+@allids+a+on+g.ID+=+a.[value]+
++++++++++++where+g.Worksite+=+@worksite)|code-block|syntax|javascript|2hjkj|当我试图保存存储过程时，它抛出了错误。我通过添加for+json路径添加到过程末尾的代码中：|fpe4a|set+@jsonout+=+(SELECT+ID,+SumLev,+Census_GEOID,+AreaName,+Worksite+
++++++++++++from+CS_GEO+G+(nolock)+
++++++++++++++++join+@allids+a+on+g.ID+=+a.[value]+
++++++++++++where+g.Worksite+=+@worksite+for+json+path)^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|M|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|O|9|@]|A|@]|B|$F|G]]]]

Just in case it helps someone, here's what caused this error for me:
I needed a procedure to return json but I left out the for json path:
<pre><code>set @jsonout = (SELECT ID, SumLev, Census_GEOID, AreaName, Worksite 
 from CS_GEO G (nolock) 
 join @allids a on g.ID = a.[value] 
 where g.Worksite = @worksite)
</code></pre>
When I tried to save the stored procedure, it threw the error. I fixed it by adding for json path to the code at the end of the procedure:
<pre><code>set @jsonout = (SELECT ID, SumLev, Census_GEOID, AreaName, Worksite 
 from CS_GEO G (nolock) 
 join @allids a on g.ID = a.[value] 
 where g.Worksite = @worksite for json path)
</code></pre>

My query is as follows, and contains a subquery within it:

<pre><code> select count(distinct dNum)
 from myDB.dbo.AQ
 where A_ID in 
 (SELECT DISTINCT TOP (0.1) PERCENT A_ID, 
 COUNT(DISTINCT dNum) AS ud 
 FROM myDB.dbo.AQ
 WHERE M &gt; 1 and B = 0 
 GROUP BY A_ID ORDER BY ud DESC)
</code></pre>

The error I am receiving is ...

<pre><code>Only one expression can be specified in the select list when the subquery is not
introduced with EXISTS.`
</code></pre>

When I run the sub-query alone, it returns just fine, so I am assuming there is some issue with the main query?

Only one expression can be specified in the select list when the subquery is not introduced with EXISTS

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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 我的查询如下所示，其中包含一个子查询： select count(distinct dNum) from myDB.dbo.AQ where A_ID in   (SELECT DISTINCT TOP (0.1) PERCENT A_ID,             COUNT(DISTINCT dNum) AS u...

问如果未使用EXISTS引入子查询，则只能在选择列表中指定一个表达式
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问如果未使用EXISTS引入子查询，则只能在选择列表中指定一个表达式EN