blocks|key|5348145|text|select+fielda,+fieldb+from+mytable+group+by+fielda+having+count(*)+>1

select+fielda,+fieldb+from+mytable+group+by+fielda+having+count(*)+=1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|5348146|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>select fielda, fieldb from mytable group by fielda having count(*) &gt;1

select fielda, fieldb from mytable group by fielda having count(*) =1
</code></pre>

blocks|key|5257744|text|对于第一个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5257745|计数(*)>1的|5257746|+SELECT+*+FROM+tbl+GROUP+BY+fielda|blockquote|5257747|5257748|5257749|对于第二个：|5257750|从tbl中选择DISTINCT(fielda)+|5257751|5257752|5257753|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|-4|5|F|7|X|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|P|$]]

For the first:

<blockquote>
 SELECT * FROM tbl GROUP BY fielda HAVING COUNT(*)>1
</blockquote>

For the second: 

<blockquote>
 SELECT DISTINCT(fielda) FROM tbl
</blockquote>

blocks|key|5348256|text|此查询对位于列表顶部的重复fieldA的表进行排序。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5348257|SELECT++a.*
FROM++++tableName+a
++++++++INNER+JOIN
++++++++(
++++++++++++SELECT+fieldA,+COUNT(*)+totalCount
++++++++++++FROM+tableName
++++++++++++GROUP+BY+fieldA
++++++++)+b+ON+a.fieldA+=+b.fieldA
ORDER+BY+b.totalCount+DESC|code-block|syntax|javascript|5348258|5348259|unordered-list-item|5348260|5348261|此查询仅选择重复记录。|5348262|SELECT++a.*
FROM++++tableName+a
++++++++INNER+JOIN
++++++++(
++++++++++++SELECT+fieldA,+COUNT(*)+totalCount
++++++++++++FROM+tableName
++++++++++++GROUP+BY+fieldA
++++++++)+b+ON+a.fieldA+=+b.fieldA
WHERE+b.totalCount+>+1
ORDER+BY+b.totalCount+DESC|5348263|5348264|5348265|5348266|这个查询选择的记录不在第二个查询中(上面)|5348267|SELECT++a.*
FROM++++tableName+a
++++++++INNER+JOIN
++++++++(
++++++++++++SELECT+fieldA,+COUNT(*)+totalCount
++++++++++++FROM+tableName
++++++++++++GROUP+BY+fieldA
++++++++)+b+ON+a.fieldA+=+b.fieldA
WHERE+b.totalCount+=+1
ORDER+BY+b.totalCount+DESC|5348268|5348269|5348270|5348271|entityMap^0|D|6|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|18|8|@]|D|@]|E|$]]|$1|L|3|-4|5|M|7|19|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1B|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]|$1|T|3|-4|5|M|7|1E|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]|$1|V|3|W|5|6|7|1G|8|@]|D|@]|E|$]]|$1|X|3|Y|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|Z|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]|$1|10|3|-4|5|M|7|1J|8|@]|D|@]|E|$]]|$1|11|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]|$1|12|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|13|$]]

This query sorts the table which duplicated <code>fieldA</code> are on top of the list.

<pre><code>SELECT a.*
FROM tableName a
 INNER JOIN
 (
 SELECT fieldA, COUNT(*) totalCount
 FROM tableName
 GROUP BY fieldA
 ) b ON a.fieldA = b.fieldA
ORDER BY b.totalCount DESC
</code></pre>

<ul>
<li><a href="http://sqlfiddle.com/#!2/5225a/1" rel="nofollow">SQLFiddle Demo</a></li>
</ul>

This query selects duplicate records only.

<pre><code>SELECT a.*
FROM tableName a
 INNER JOIN
 (
 SELECT fieldA, COUNT(*) totalCount
 FROM tableName
 GROUP BY fieldA
 ) b ON a.fieldA = b.fieldA
WHERE b.totalCount &gt; 1
ORDER BY b.totalCount DESC
</code></pre>

<ul>
<li><a href="http://sqlfiddle.com/#!2/5225a/2" rel="nofollow">SQLFiddle Demo</a></li>
</ul>

and this one, selects records which are not on the second query (above)

<pre><code>SELECT a.*
FROM tableName a
 INNER JOIN
 (
 SELECT fieldA, COUNT(*) totalCount
 FROM tableName
 GROUP BY fieldA
 ) b ON a.fieldA = b.fieldA
WHERE b.totalCount = 1
ORDER BY b.totalCount DESC
</code></pre>

<ul>
<li><a href="http://sqlfiddle.com/#!2/5225a/3" rel="nofollow">SQLFiddle Demo</a></li>
</ul>

The question is for the example table structure:

mytable

<pre><code>fielda, fieldb
val1 valx
val2 valy
val3 valz
val1 vala
</code></pre>

I want to select from mytable with a query:

<pre><code>fielda, fieldb
val1 valx
val1 vala
</code></pre>

basically select * from table where fielda is duplicated.

then with a different query select from mytable

<pre><code>fielda, fieldb
val2 valy
val3 valz
</code></pre>

val1 on fielda was encountered as a duplicate therefore it wasn't selected and the rest were.

select * duplicates, then select * non-duplicates - 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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问题是关于示例表结构的：mytablefielda, fieldbval1    valxval2    valyval3    valzval1    vala我想用一个查询从mytable中选择：fielda, fieldbval1    valxval1    vala基本上是从复制了fielda的表中选择*。然...

问选择复制，然后选择非复制- mysql
EN

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问选择*复制，然后选择*非复制- mysqlEN