在nodeJS和MongoDb中的集合中找到最大值

Question

我有一个非常简单的查询，但无法正常工作。 我有一个名为users的集合，该集合具有uid字段。 我想从中获取uid字段的最大值。 以下是我的工作：-

   var options = { "sort": [['uid',-1]] };
    db.users.findOne({}, options , function(err, doc) {
    console.log("Returned #" + doc.uid + " documents");
}); 

但这给了我99，而我的值最多为300。我猜它是将每个元素都匹配为9，然后进行比较。 正确答案应该是314

以下是将条目保存在集合中的方式：-

{ 
 {
 _id: "531181a3ec9af9107d2b4ccd",
 age: "0",
 carModel: "bullet motorcycle",
 chargePrice: "",
 contact: "",
 email: "",
 fbid: "1179803227",
 fromLat: "28.4594965",
 fromLon: "77.0266383",
 fromName: "Gurgaon, Haryana, India",
 fuelType: "Petrol",
 id: "215",
 image: "http://graph.facebook.com/1179803227/picture?type=large",
 name: "Sandeep Yadav",
 points: "0",
 regid: "abc",
 returnTime: "15:41 Hrs",
 sex: "0", 
 smoking: "No Smoking allowed",
 startTime: "15:41 Hrs",
 toLat: "28.510782",
 toLon: "77.048646",
 toName: "Sector 23 ,HUDA Market, Huda, Sector 23, Gurgaon, Haryana, India",
 uid: 311
},
{
 _id: "531181a3ec9af9107d2b4cce",
 age: "0",
 carModel: "2014 Nissan sentra",
 chargePrice: "USD 30",
 contact: "",
 email: "",
 fbid: "100001451156666",
 fromLat: "27.950575",
 fromLon: "-82.4571776",
 fromName: "Tampa, FL, United States",
 fuelType: "Petrol",
 id: "214",
 image: "http://graph.facebook.com/100001451156666/picture?type=large",
 name: "Kelly J. Dugan",
 points: "0",
 regid: "abc",
 returnTime: "23:04 Hrs",
 sex: "0",
 smoking: "Doesnt Matter",
 startTime: "16:02 Hrs",
 toLat: "25.7889689",
 toLon: "-80.2264393",
 toName: "Miami, FL, United States",
 uid: 308
}
}

Answer 1

尝试这个：

db.users.find({}).sort("uid":-1).limit(1)

会找到所有用户，然后对其进行排序，然后只返回第一个用户。