Question

my Jobs is like below

{
    "_id" : ObjectId("5b6979339bcdb5d4ae64498f"),
    "jobProfile" : "Java Developer",
    "jobID" : "1",
    "companyName" : "xyz",
    "openingsCount" : 10,
    "jobType" : "Fulltime",
    "jobDescription" : "profile description",
    "contactEmail" : "xyz@gmail.com",
    "contactWebsite" : "www.xyz.com",
    "postingDate" : "07-08-2018 04:21:22",
    "jobstatus" : "Active",
    "jobEndDate" : ISODate("2018-08-14T23:59:59.999Z"),
    "jobEndDateMilliSeconds" : 1534204859999.0
}


{
    "_id" : ObjectId("5b6aba4c9bcdb5d4ae649197"),
    "jobProfile" : "Python Developer",
    "jobID" : "2",
    "companyName" : "abc",
    "openingsCount" : 10,
    "jobType" : "Fulltime",
    "jobDescription" : "profile description",
    "contactEmail" : "abc@gmail.com",
    "contactWebsite" : "www.abc.com",
    "postingDate" : "07-08-2018 04:21:22",
    "jobstatus" : "Active",
    "jobEndDate" : ISODate("2018-08-14T23:59:59.999Z"),
    "jobEndDateMilliSeconds" : 1534204859000.0
}

和我的Shortlistjobs集合在下面

{
    "_id" : ObjectId("5b6abaaf9bcdb5d4ae6491d2"),
    "jobID" : "1",
    "jobstatus" : "Active",
    "applicantsCount" : 10
}


{
    "_id" : ObjectId("5b6ababc9bcdb5d4ae6491f2"),
    "jobID" : "2",
    "jobstatus" : "Active",
    "applicantsCount" : 8
}


{
    "_id" : ObjectId("5b6abac59bcdb5d4ae6491f8"),
    "jobID" : "3",
    "jobstatus" : "Active",
    "applicantsCount" : 8
}

我希望所有在Jobs集合中存在的工作都与Shortlistjobs集合中的申请人数一起出现。从Shortlistjobs集合到Jobs集合文档中只能包含一个字段。

我想要如下输出：

{
    "_id" : ObjectId("5b6979339bcdb5d4ae64498f"),
    "jobProfile" : "Java Developer",
    "jobID" : "1",
    "companyName" : "xyz",
    "openingsCount" : 10,
    "jobType" : "Fulltime",
    "jobDescription" : "profile description",
    "contactEmail" : "xyz@gmail.com",
    "contactWebsite" : "www.xyz.com",
    "postingDate" : "07-08-2018 04:21:22",
    "jobstatus" : "Active",
    "jobEndDate" : ISODate("2018-08-14T23:59:59.999Z"),
    "jobEndDateMilliSeconds" : 1534204859999.0,
 "applicantsCount" : 10
}


{
    "_id" : ObjectId("5b6aba4c9bcdb5d4ae649197"),
    "jobProfile" : "Python Developer",
    "jobID" : "2",
    "companyName" : "abc",
    "openingsCount" : 10,
    "jobType" : "Fulltime",
    "jobDescription" : "profile description",
    "contactEmail" : "abc@gmail.com",
    "contactWebsite" : "www.abc.com",
    "postingDate" : "07-08-2018 04:21:22",
    "jobstatus" : "Active",
    "jobEndDate" : ISODate("2018-08-14T23:59:59.999Z"),
    "jobEndDateMilliSeconds" : 1534204859000.0,,
 "applicantsCount" : 8
}

我正在使用以下查询

db.Jobs.aggregate([
{ $match : {jobstatus:"Active"}},

{ $lookup:
 {
   from        : "Shortlistjobs",
   localField  : "jobID",
   foreignField: "jobID",
   as          : "meta"
 }
},

{
 $unwind: {
               path : "$meta"
           }
       },
        {
           $sort: {
             'meta.applicantsCount':-1
           }
       },{$limit:1}

])

以下我从上述查询中得到的输出

{
    "_id" : ObjectId("5b6979339bcdb5d4ae64498f"),
    "jobProfile" : "Java Developer",
    "jobID" : "1",
    "companyName" : "IAAA Technologies",
    "jobCity" : "Bangalore",
    "jobCountry" : "India",
    "openingsCount" : 10,
    "jobType" : "Fulltime",
    "jobDescription" : "profile description",
    "contactEmail" : "iaaatech@gmail.com",
    "contactWebsite" : "www.iaaatech.com",
    "postingDate" : "07-08-2018 04:21:22",
    "jobstatus" : "Active",
    "jobEndDate" : ISODate("2018-08-14T23:59:59.999Z"),
    "jobEndDateMilliSeconds" : 1534204859999.0,
    "meta" : {
        "_id" : ObjectId("5b6abaaf9bcdb5d4ae6491d2"),
        "jobID" : "1",
        "jobstatus" : "Active",
        "applicantsCount" : 10
    }
}

Answer 1

您可以使用$project从嵌套对象中使用（$addFields）和所有其他必填字段来添加特定字段：

db.Jobs.aggregate([
{$lookup:{ from: 'Shortlistjobs ', localField: 'jobID', foreignField: "jobID", as: "meta"  }},
{$unwind: "$meta"}, 
{$addFields: { "applicantsCount": "$meta.applicantsCount"}}, 
{$project:{meta:0}}])

两个集合之间的mongo查询

1 个答案: