mongodb 使用mongodb在数组中查找子文档
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Find Subdocument in Array with mongodb
提问by mritz_p
I am playing around with the The bios Example Collection from http://docs.mongodb.org/manual/reference/bios-example-collectionto educate myself about querying mongodb.
我正在使用http://docs.mongodb.org/manual/reference/bios-example-collection 中的 bios 示例集合来教育自己查询 mongodb。
I want to retrieve informations about the awards won by _id : 1in year : 1975.
我想检索有关_id : 1在1975 年获得的奖项的信息。
I tried several queries, among those
我尝试了几个查询，其中
bios.find({
"_id" : 1,
"awards" : {
"year" : 1975
}
});
but I never receive the proper document back. How can I retrieve this document in the array?
但我从来没有收到正确的文件回来。如何在数组中检索此文档？
回答by mnemosyn
You have to use the dot notation:
您必须使用点符号：
bios.find({"_id" : 1, "awards.year" : 1975 });
It's a rather pointless query, because you also have the _idin the query, but I guess that's due to the fact that you're playing with an example. Also, you're saying you're looking for awards from 1967, but the code says 1975.
这是一个相当无意义的查询，因为您_id在查询中也有，但我想这是因为您正在玩一个例子。另外，您是说您正在寻找 1967 年的奖项，但代码显示是 1975 年。
If you search for "awards" : { "year" : 1975 }, mongodb will look for an exact match of the entire subdocument awards. In this case, that is not what you want. Also, since awardsis an array, this will always be false. If you wanted to look up a specific award document in a list, $elemMatchwould be the way to go.
如果您搜索"awards" : { "year" : 1975 }，mongodb 将查找整个子文档的完全匹配awards。在这种情况下，这不是您想要的。此外，由于awards是一个数组，这将始终为假。如果您想在列表中查找特定的奖励文件，$elemMatch这将是您要走的路。
