在mongodb中按汇总请求按日期排序 [英] sort by date with aggregate request in mongodb

问题描述

我想检索当前已签署的最旧文档的值列表，但是我未能选择该日期缺席的文档.谢谢

I would like to retrieve a list of values ​​that comes from the oldest document currently signed.But i failed to select a document absed on the date.Thanks

这是json:

    "ad" : "noc3",
    "createdDate" : ISODate(),
    "list" : [
            {
                    "id" : "p45",
                    "value" : 21,

            },
            {
                    "id" : "p6",
                    "value" : 20,             
            },
            {
                   "id" : "4578",     
                    "value" : 319
            }
   ]

这是我的汇总请求:

db.friends.aggregate({$match:{advertiser:"noc3", {$sort:{timestamps:-1},{$limit:1} }},{$unwind:"$list"},{$project:{_id: "$list.id", value:{$add:[0]}}});

推荐答案

您的汇总查询不正确.您将排序和限制添加到匹配项中，但这就是您的操作方式.您使用不同的管道运算符:

Your aggregate query is incorrect. You add the sort and limit to the match, but that's now how you do that. You use different pipeline operators:

db.friends.aggregate( [
    { $match: { advertiser: "noc3" } }, 
    { $sort: { createdDate: -1 } },
    { $limit: 1 },

您的其他管道运算符也有些奇怪，并且您的代码与查询在timestamps与createdDate上不匹配.如果您添加了预期的输出，那么我也可以更新答案以包括查询的最后几位.

Your other pipeline operators are bit strange too, and your code vs query mismatches on timestamps vs createdDate. If you add the expected output, I can update the answer to include the last bits of the query too.

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