blocks|key|1409464|text|谢谢!这是一个展示CouchDB+0.11的新特性的很好的例子！|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1409465|必须使用与获取相关的数据特性来引用视图中的文档。为了获得更方便的JSON，可以选择使用_list函数来清理结果。详情请参见库奇奥对“加入”的评论。|style|BOLD|CODE|1409466|计划如下：|1409467|首先，您对el文档有一个唯一性限制。如果他们中的两个有id=2，那就是个问题。如果是_id，则有必要使用id字段。CouchDB将保证唯一性，但该计划的其余部分需要_id才能通过ID获取文档。
{“类型”："el“、"_id”："1“、”内容“："first”}{type+"type“："el”、"_id“："2”、"content“："second”{}{+"type“："el”、"_id“："3”、“_id”："content“："third”}
如果完全不可能将文档更改为使用_id，则可以为emit(doc.id,+doc)创建一个简单的视图，然后将其重新插入到临时数据库中。这将id转换为_id，但也增加了一些复杂性。|ordered-list-item|1409468|视图发出{"_id":+content_id}数据，按[list_id,+sort_number]键，将列表与其内容“分组”。
函数(Doc){+if(doc.type+==+'list')+{+for+(var+i+in+doc.elements)+{+//链接到el文档的id。var+id+=+doc.elementsi；emit(doc.id，i，{'_id'：id})；}}
现在有一个简单的el文档列表，按正确的顺序排列。如果只想看到特定的列表，可以使用startkey和endkey。
curl+localhost:5984/x/_design/myapp/_view/els+{"total_rows":2，“偏移”：0，“行”：[{“id”：“036f3614aeee05344aeee05344cdfb66fa1002db6”、“abc123”、“abc123”、"0“、”值“：{”_id“：”2“}}、{”id“：”036f3614aee05344cdfb662db6“、”键“：”abc123“、"1”、“值”：{“_id”：“1”}|1409469|要获取el内容，请使用include_docs=true查询。通过_id的魔力，el文档将加载。
curl+localhost:5984/x/_design/myapp/_view/els?include_docs=true+{"total_rows":2，“偏移”：0，“行”：[+{"id":"036f3614aeee05344cdfb66fa1002db6"，“键”：“abc123”，"0"，“值”：{“_id”：“2”}，"doc":{"_id":"2"，“_rev”：“_id”：“2”，“_rev”：“1-4530dc6946dc6946d78f1e97f56568de585d9”，“type”类型：“el”，“_id”：“_id”：“second”}}，{"id":"036f3614aeee05344cdfb66fa1002db6"，"key":"abc123"，"1"，"value":{"_id":"1"}，"doc":{"_id":"1"，"_rev":"1-852badd683f22ad4705ed9fcdea5b814"，"type":"el"，“_id”：“_id”：“first”}
注意，这已经是您需要的所有信息了。如果您的客户端是灵活的，您可以解析这个JSON中的信息。下一个可选步骤只是重新格式化它，以匹配您需要的内容。|1409470|使用_list函数，它简单地重新格式化视图输出。人们使用它们输出XML或HTML，但是我们将使JSON更方便。
函数(head，req)+{+var+headers+=+{'content'：'application/json'}；var结果；if(req.query.include_docs+!=+'true')+{+start({'code'：400，headers:+headers})；require+={‘include_docs=true'}；}+else+{start({headers’：headers})；结果={‘include_docs=true’内容：[]}；while(row+=+getRow())+{+result.content.push(row.doc.content)；}send(JSON.stringify(结果))；}
结果吻合。当然，在生产中，您需要startkey和endkey来指定您想要的列表。
curl+'localhost:5984/x/_design/myapp/_list/pretty/els?include_docs=true&startkey="abc123"，“&endkey=”abc123，{}+{"content":"second"，"first"}|1409471|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/2683146/what-are-the-major-new-features-of-couchdb-0-11|1|http://blog.couchbase.com/whats-new-in-apache-couchdb-0-11-part-two-views^0|9|G|0|0|0|21|17|5|1P|B|1|0|0|5|0|0|2O|2P|3M|6C|2G|5|2|16|3|1G|2|2A|3|6R|3|6Z|H|88|2|8D|3|0|0|1R|1S|3K|5D|1K|6Y|6E|4|J|R|M|5L|2|6H|8|6Q|6|0|0|1C|1D|CS|E6|1Z|3|2|B|H|X|3|14|2|0|0|1J|1K|91|AM|15|BS|3U|2|5|B2|8|BB|6|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@$A|14|B|15|1|16]]|C|$]]|$1|D|3|E|5|6|7|17|8|@$A|18|B|19|F|G]|$A|1A|B|1B|F|H]]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|I|3|J|5|6|7|1F|8|@$A|1G|B|1H|F|G]]|9|@]|C|$]]|$1|K|3|L|5|M|7|1I|8|@$A|1J|B|1K|F|G]|$A|1L|B|1M|F|G]|$A|1N|B|1O|F|G]|$A|1P|B|1Q|F|H]|$A|1R|B|1S|F|H]|$A|1T|B|1U|F|H]|$A|1V|B|1W|F|H]|$A|1X|B|1Y|F|H]|$A|1Z|B|20|F|H]|$A|21|B|22|F|H]|$A|23|B|24|F|H]]|9|@]|C|$]]|$1|N|3|O|5|M|7|25|8|@$A|26|B|27|F|G]|$A|28|B|29|F|G]|$A|2A|B|2B|F|G]|$A|2C|B|2D|F|G]|$A|2E|B|2F|F|H]|$A|2G|B|2H|F|H]|$A|2I|B|2J|F|H]|$A|2K|B|2L|F|H]|$A|2M|B|2N|F|H]]|9|@]|C|$]]|$1|P|3|Q|5|M|7|2O|8|@$A|2P|B|2Q|F|G]|$A|2R|B|2S|F|G]|$A|2T|B|2U|F|G]|$A|2V|B|2W|F|H]|$A|2X|B|2Y|F|H]|$A|2Z|B|30|F|H]|$A|31|B|32|F|H]]|9|@]|C|$]]|$1|R|3|S|5|M|7|33|8|@$A|34|B|35|F|G]|$A|36|B|37|F|G]|$A|38|B|39|F|G]|$A|3A|B|3B|F|G]|$A|3C|B|3D|F|H]|$A|3E|B|3F|F|H]|$A|3G|B|3H|F|H]]|9|@]|C|$]]|$1|T|3|-4|5|6|7|3I|8|@]|9|@]|C|$]]]|U|$V|$5|W|X|Y|C|$Z|10]]|11|$5|W|X|Y|C|$Z|12]]]]

Thank you! This is a great example to show off <a href="https://stackoverflow.com/questions/2683146/what-are-the-major-new-features-of-couchdb-0-11">CouchDB 0.11's new
features</a>!

You must use the fetch-related-data feature to reference documents
in the view. Optionally, for more convenient JSON, use a <code>_list</code> function to
clean up the results. See <a href="http://blog.couchbase.com/whats-new-in-apache-couchdb-0-11-part-two-views" rel="nofollow noreferrer">Couchio's writeup on "JOIN"s</a> for details.

Here is the plan:

<ol>
<li>Firstly, you have a uniqueness contstraint on your <code>el</code> documents. If two of
them have id=2, that's a problem. It is necessary to use
the <code>_id</code> field instead if <code>id</code>. CouchDB will guarantee uniqueness, but also,
the rest of this plan requires <code>_id</code> in order to fetch documents by ID.

<pre><code>{ "type" : "el", "_id" : "1", "content" : "first" } 
{ "type" : "el", "_id" : "2", "content" : "second" } 
{ "type" : "el", "_id" : "3", "content" : "third" } 
</code></pre>

If changing the documents to use <code>_id</code> is absolutely impossible, you can
create a simple view to <code>emit(doc.id, doc)</code> and then re-insert that into a
temporary database. This converts <code>id</code> to <code>_id</code> but adds some complexity.</li>
<li>The view emits <code>{"_id": content_id}</code> data keyed on
<code>[list_id, sort_number]</code>, to "clump" the lists with their content.

<pre><code>function(doc) {
 if(doc.type == 'list') {
 for (var i in doc.elements) {
 // Link to the el document's id.
 var id = doc.elements[i];
 emit([doc.id, i], {'_id': id});
 }
 }
}
</code></pre>

Now there is a simple list of <code>el</code> documents, in the correct order. You can
use <code>startkey</code> and <code>endkey</code> if you want to see only a particular list.

<pre><code>curl localhost:5984/x/_design/myapp/_view/els
{"total_rows":2,"offset":0,"rows":[
{"id":"036f3614aeee05344cdfb66fa1002db6","key":["abc123","0"],"value":{"_id":"2"}},
{"id":"036f3614aeee05344cdfb66fa1002db6","key":["abc123","1"],"value":{"_id":"1"}}
]}
</code></pre></li>
<li>To get the <code>el</code> content, query with <code>include_docs=true</code>. Through the magic of
<code>_id</code>, the <code>el</code> documents will load.

<pre><code>curl localhost:5984/x/_design/myapp/_view/els?include_docs=true
{"total_rows":2,"offset":0,"rows":[
{"id":"036f3614aeee05344cdfb66fa1002db6","key":["abc123","0"],"value":{"_id":"2"},"doc":{"_id":"2","_rev":"1-4530dc6946d78f1e97f56568de5a85d9","type":"el","content":"second"}},
{"id":"036f3614aeee05344cdfb66fa1002db6","key":["abc123","1"],"value":{"_id":"1"},"doc":{"_id":"1","_rev":"1-852badd683f22ad4705ed9fcdea5b814","type":"el","content":"first"}}
]}
</code></pre>

Notice, this is already all the information you need. If your client is
flexible, you can parse the information out of this JSON. The next optional
step simply reformats it to match what you need.</li>
<li>Use a <code>_list</code> function, which simply reformats the view output. People use them to output XML or HTML however we will make
the JSON more convenient.

<pre><code>function(head, req) {
 var headers = {'Content-Type': 'application/json'};
 var result;
 if(req.query.include_docs != 'true') {
 start({'code': 400, headers: headers});
 result = {'error': 'I require include_docs=true'};
 } else {
 start({'headers': headers});
 result = {'content': []};
 while(row = getRow()) {
 result.content.push(row.doc.content);
 }
 }
 send(JSON.stringify(result));
}
</code></pre>

The results match. Of course in production you will need <code>startkey</code> and <code>endkey</code> to specify the list you want.

<pre><code>curl -g 'localhost:5984/x/_design/myapp/_list/pretty/els?include_docs=true&amp;startkey=["abc123",""]&amp;endkey=["abc123",{}]'
{"content":["second","first"]}
</code></pre></li>
</ol>

I am looking for a CouchDB equivalent to "SQL joins".

In my example there are CouchDB documents that are list elements:

<pre><code>{ "type" : "el", "id" : "1", "content" : "first" } 
{ "type" : "el", "id" : "2", "content" : "second" } 
{ "type" : "el", "id" : "3", "content" : "third" } 
</code></pre>

There is one document that defines the list:

<pre><code>{ "type" : "list", "elements" : ["2","1"] , "id" : "abc123" }
</code></pre>

As you can see the third element was deleted, it is no longer part of the list. So it must not be part of the result. Now I want a view that returns the content elements including the right order. 

The result could be:

<pre><code>{ "content" : ["second", "first"] }
</code></pre>

In this case the order of the elements is already as it should be. Another possible result:

<pre><code>{ "content" : [{"content" : "first", "order" : 2},{"content" : "second", "order" : 1}] }
</code></pre>

I started writing the map function:

<pre><code>map = function (doc) {
 if (doc.type === 'el') {
 emit(doc.id, {"content" : doc.content}); //emit the id and the content
 exit;
 }
 if (doc.type === 'list') {
 for ( var i=0, l=doc.elements.length; i&lt;l; ++i ){
 emit(doc.elements[i], { "order" : i }); //emit the id and the order
 }
 }
}
</code></pre>

This is as far as I can get. Can you correct my mistakes and write a reduce function? Remember that the third document must not be part of the result.

Of course you can write a different map function also. But the structure of the documents (one definig element document and an entry document for each entry) cannot be changed.

<hr>

EDIT: Do not miss JasonSmith's comment to his answer, where he describes how to do this shorter.

Best way to do one-to-many "JOIN" in CouchDB

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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我正在寻找一个相当于"SQL“的CouchDB。在我的示例中，有一些CouchDB文档是列表元素：{ "type" : "el", "id" : "1", "content" : "first" } { "type" : "el", "id" : "2", "content" : "second" } { "type"...

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