MongoDB排序查询？

Question

db.data.insert({userAjax: 'sean',date:'26/04/2014',latv:'78.134123', lonv:'43.
342123', distance:'1.23', hours:'0', minutes:'4', seconds:'21', speed: '1.04' })

db.data.insert({userAjax: 'sean',date:'26/04/2014',latv:'78.134123', lonv:'43.
342123', distance:'1.23', hours:'0', minutes:'4', seconds:'21', speed: '1.04' })

db.data.insert({userAjax: 'sean',date:'25/04/2014',latv:'78.134123', lonv:'43.
342123', distance:'0.43', hours:'0', minutes:'2', seconds:'47', speed: '1.33' })

db.data.insert({userAjax: 'sean',date:'25/04/2014',latv:'78.134123', lonv:'43.
342123', distance:'0.43', hours:'0', minutes:'7', seconds:'55', speed: '1.33' })

这是我收藏的示例结构。在网站上我需要显示日期，但只显示该日期的最新插入，

数据通过 ajax 从手机（地理位置）传来，在客户端必须显示插入的最新日期。

Answer 1

你大概是按日期为给定用户排序的：

db.data.find({ "userAjax": "sean" }).sort({ "date": -1 }).limit(1)

只为您提供该用户在最近日期的一个结果。

另一方面，如果您正在寻找每天的最后一个结果，那么您可以借助 .aggregate() 函数：

db.data.aggregate([
    { "$match": { "userAjax": "sean" } },
    { "$project": {
        "_id": { 
            "date": {
                "year": { "$year": "$date" },
                "month": { "$month": "$date" },
                "day": { "$dayOfMonth": "$date" }
            }
        },
        "userAjax": "$userAjax",
        "date": "$date",
        "latv": "$latv", 
        "lonv": "$longv", 
        "distance": "$distance", 
        "hours": "$hours",
        "minutes": "$minutes", 
        "seconds": "$seconds", 
        "speed": "$speed" 
    }},
    { "$sort": { "_id": -1 } },
    { "$group": {
        "_id": { "$first": "$_id" },
        "userAjax": { "$first": "$userAjax" },
        "date": { "$first": "$date" },
        "latv": { "$first": "$latv" }, 
        "lonv": { "$first": "$longv" },
        "distance": { "$first": "$distance" },
        "hours": { "$first": "$hours" },
        "minutes": { "$first": "$minutes" }, 
        "seconds": { "$first": "$seconds" }, 
        "speed": { "$first": "$speed" }
    }}
])

这更简洁，但这就是你想要的。