如何在mongodb中查询对象的嵌套数组？

Arun Yegi 发表于 Dev

阿伦·耶吉

我试图从节点js查询mongodb中的嵌套对象数组，尝试了所有解决方案，但没有运气。谁能帮忙呢？

我试过以下：

{
              "name": "Science",
              "chapters": [
                 {
                     "name": "ScienceChap1",
                     "tests": [
                        {
                            "name": "ScienceChap1Test1",
                            "id": 1,
                            "marks": 10,
                            "duration": 30,
                            "questions": [
                               {
                                   "question": "What is the capital city of New Mexico?",
                                   "type": "mcq",
                                   "choice": [
                                      "Guadalajara",
                                      "Albuquerque",
                                      "Santa Fe",
                                      "Taos"
                                   ],
                                   "answer": [
                                      "Santa Fe",
                                      "Taos"
                                   ]
                               },
                               {
                                   "question": "Who is the author of beowulf?",
                                   "type": "notmcq",
                                   "choice": [
                                      "Mark Twain",
                                      "Shakespeare",
                                      "Abraham Lincoln",
                                      "Newton"
                                   ],
                                   "answer": [
                                      "Shakespeare"
                                   ]
                               }
                            ]
                        },
                        {
                            "name": "ScienceChap1test2",
                            "id": 2,
                            "marks": 20,
                            "duration": 30,
                            "questions": [
                               {
                                   "question": "What is the capital city of New Mexico?",
                                   "type": "mcq",
                                   "choice": [
                                      "Guadalajara",
                                      "Albuquerque",
                                      "Santa Fe",
                                      "Taos"
                                   ],
                                   "answer": [
                                      "Santa Fe",
                                      "Taos"
                                   ]
                               },
                               {
                                   "question": "Who is the author of beowulf?",
                                   "type": "notmcq",
                                   "choice": [
                                      "Mark Twain",
                                      "Shakespeare",
                                      "Abraham Lincoln",
                                      "Newton"
                                   ],
                                   "answer": [
                                      "Shakespeare"
                                   ]
                               }
                            ]
                        }
                     ]
                 }
              ]
          }

到目前为止，这是我尝试过的方法，但仍然无法正常工作

db.quiz.find({name:"Science"},{"tests":0,chapters:{$elemMatch:{name:"ScienceCh‌ap1"}}})
db.quiz.find({ chapters: { $elemMatch: {$elemMatch: { name:"ScienceChap1Test1" } } }}) 
db.quiz.find({name:"Science"},{chapters:{$elemMatch:{$elemMatch:{name:"Scienc‌eChap1Test1"}}}}) ({ name:"Science"},{ chapters: { $elemMatch: {$elemMatch: { name:"ScienceChap1Test1" } } }})

阿卜杜拉·拉希德（Abdullah Rasheed）

汇总框架

您可以使用聚合框架来转换和合并集合中的文档以显示给客户端。您建立了一个通过多个构建块来处理文档流的管道：过滤，投影，分组，排序等。

如果要从名为“ ScienceChap1Test1”的测试中获得mcq类型的问题，请执行以下操作：

db.quiz.aggregate(
    //Match the documents by query. Search for science course
    {"$match":{"name":"Science"}},

    //De-normalize the nested array of chapters.
    {"$unwind":"$chapters"},
    {"$unwind":"$chapters.tests"},

    //Match the document with test name Science Chapter
    {"$match":{"chapters.tests.name":"ScienceChap1test2"}},

    //Unwind nested questions array
    {"$unwind":"$chapters.tests.questions"},

    //Match questions of type mcq
    {"$match":{"chapters.tests.questions.type":"mcq"}}
).pretty()

结果将是：

{
    "_id" : ObjectId("5629eb252e95c020d4a0c5a5"),
    "name" : "Science",
    "chapters" : {
        "name" : "ScienceChap1",
        "tests" : {
            "name" : "ScienceChap1test2",
            "id" : 2,
            "marks" : 20,
            "duration" : 30,
            "questions" : {
                "question" : "What is the capital city of New Mexico?",
                "type" : "mcq",
                "choice" : [
                    "Guadalajara",
                    "Albuquerque",
                    "Santa Fe",
                    "Taos"
                ],
                "answer" : [
                    "Santa Fe",
                    "Taos"
                ]
            }
        }
    }
}