通过匹配日期元素和MongoDb中嵌套数组的其他元素的最大值来获取集合答案

【问题标题】：Get collection by matching date element and max value of other element of a nested array in MongoDb通过匹配日期元素和MongoDb中嵌套数组的其他元素的最大值来获取集合
【发布时间】：2015-12-06 21:00:39
【问题描述】：

我有一个名为“plan”的 mongodb 集合，其中包含嵌套文档，如下所示：

//1 {
"_id" : ObjectId("55ed97c91ed85902375f60c3"),
"createdAt" : ISODate("2015-09-07T13:57:29.700Z"),
"suggestions" : [ 
    {
        "title" : "First suggestion",
        "vote" : 5,
        "_id" : ObjectId("55ed97c91ed85902375f60c5"),
        "createdAt" : ISODate("2015-09-07T13:57:29.701Z"),
        "startDate" : ISODate("2015-09-02T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-05T13:57:29.701Z")
    }, 
    {
        "title" : "second suggestion",
        "vote" : 8,
        "_id" : ObjectId("55ed97c91ed85902375f60c4"),
        "createdAt" : ISODate("2015-09-07T13:57:29.701Z"),
        "startDate" : ISODate("2015-09-07T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-10T13:57:29.701Z")
    }
],
"__v" : 0

//2 {
"_id" : ObjectId("55f1570fd86512e01f4d55c8"),
"createdAt" : ISODate("2015-09-10T10:10:23.381Z"),
"suggestions" : [ 
    {
        "title" : "First suggestion",
        "vote" : 3,
        "startDate" : ISODate("2015-09-10T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-15T13:57:29.701Z"),
        "_id" : ObjectId("55f1570fd86512e01f4d55ca"),
        "createdAt" : ISODate("2015-09-10T10:10:23.381Z")
    }, 
    {
        "title" : "second suggestion",
        "vote" : 2,
        "startDate" : ISODate("2015-09-02T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-04T13:57:29.701Z"),
        "_id" : ObjectId("55f1570fd86512e01f4d55c9"),
        "createdAt" : ISODate("2015-09-10T10:10:23.381Z")
    }
],
"__v" : 0

}

而且我必须收集“suggestions.endDate”小于“ISODate(”2015-09-07T13:57:29.701Z")”的集合，并且“投票”在集合中的所有建议中应该更大。我只期待这个：

       //1 {
"_id" : ObjectId("55ed97c91ed85902375f60c3"),
"createdAt" : ISODate("2015-09-07T13:57:29.700Z"),
"suggestions" : [ 
    {
        "title" : "First suggestion",
        "vote" : 5,
        "_id" : ObjectId("55ed97c91ed85902375f60c5"),
        "createdAt" : ISODate("2015-09-07T13:57:29.701Z"),
        "startDate" : ISODate("2015-09-02T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-05T13:57:29.701Z")
    }, 
    {
        "title" : "second suggestion",
        "vote" : 8,
        "_id" : ObjectId("55ed97c91ed85902375f60c4"),
        "createdAt" : ISODate("2015-09-07T13:57:29.701Z"),
        "startDate" : ISODate("2015-09-07T13:57:29.701Z"),
        "endDate" : ISODate("2015-09-10T13:57:29.701Z")
    }
],
"__v" : 0

这是我正在使用的查询：

        db.plan.aggregate([{$match: {suggestions: {$elemMatch: {endDate: {$lt: ISODate("2015-09-07T13:57:29.701Z")}}}}}, {$sort: {"suggestions.vote": -1}}]).pretty()

但这对我不起作用，它只是匹配日期。我是 MongoDb 的新手？有什么帮助吗？谢谢。

【问题讨论】：

标签： node.js mongodb mongoose mongodb-query

【解决方案1】：

试试下面的查询，它会工作的

db.plan.aggregate(
        [
            {
                $match: {
                    "suggestions.endDate": {
                        $lt: ISODate("2015-09-10T13:57:29.701Z")
                    }
                }
            },
            {
                "$sort": {
                    "suggestions.vote": -1
                }
            },
            {
                $limit: 1
            }
        ]
).pretty();

【讨论】：