查詢的MongoDB與DBREF

Question

我在蒙戈數據庫的表中調用文件

{ 
    "_id" : ObjectId("565a7f1"), 
    "_class" : "Document", "name" : 
    "Book Template", 
    "location" : "/Book Template.pdf", 
    "type" : DBRef("types", ObjectId("3eaabf5")) 
}, 
{ 
    "_id" : ObjectId("565a7f2), 
    "_class" : "Document", 
    "name" : "Sample Contract", 
    "location" : "/Sample Contract.pdf", 
    "type" : DBRef("types", ObjectId("3eaabf5")) 
}, 
{ 
    "_id" : ObjectId("565a7f3"), 
    "_class" : "Document", 
    "name" : "Clustering with RabbitMQ", 
    "location" : "/Clustering with RabbitMQ.txt", 
    "type" : DBRef("types", ObjectId("3eaabf6")) 
} 

，然後我也被稱爲表類型

{ 
    "_id" : ObjectId("3eaabf5"), 
    "_class" : "Type", 
    "name" : "PDF", 
    "description" : "Portable Document Format", 
    "extension" : ".pdf" 
}; 
{ 
    "_id" : ObjectId("3eaabf6"), 
    "_class" : "Type", 
    "name" : "NOTE", 
    "description" : "Text Notes", 
    "extension" : ".txt" 
}, 
{ 
    "_id" : ObjectId("3eaabf7"), 
    "_class" : "Type", 
    "name" : "WEB", 
    "description" : "Web Link", 
    "extension" : ".url" 
} 

我要查詢的文件表裏面有所有的文件PDF的擴展。

所以我寫了下面的查詢......但一切都返回空結果。

>db.documents.find({"types.$id":"3eaabf5"}) 
> 
>db.documents.find({"types.name":"PDF"}) 
> 

Answer 1

你可以試試這個

db.documents.find({"type.$id":ObjectId("3eaabf5")}