MongoDB 之 Find查询

Find查询是MongoDB中最基本也是最常用的语法。使用起来也非常简单。下面列出了Find的一些基本操作。

> db.news.find()  //select * from [news]

{ "_id" : 10001, "count" : 1, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:40:58.034Z") }

{ "_id" : 10002, "count" : 2, "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:41:57.860Z") }

{ "_id" : 10003, "count" : 3, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:42:09.794Z") }

{ "_id" : 10004, "count" : 4, "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:42:19.185Z") }

{ "_id" : 10005, "count" : 5, "news" : "new a good day", "time" : ISODate("2011-09-05T13:42:36.860Z") }

> db.news.findOne() //select top 1 * from [news]

{ "_id" : 10001, "count" : 1, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:40:58.034Z") }

> db.news.find({"_id":10001,"count":1})  //select * from [news] where _id=10001 and count=1

{ "_id" : 10001, "count" : 1, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:40:58.034Z") }

> db.news.find({"count":{"$gt":2,"$lte":4}})  //select * from [news] where count>2 and  count<=4

{ "_id" : 10003, "count" : 3, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:42:09.794Z") }

{ "_id" : 10004, "count" : 4, "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:42:19.185Z") }

> stime = new Date()

ISODate("2011-09-05T13:57:21.812Z")

> db.news.find({"time":{"$lt":stime}}) //select * from news where time<ISODate("2011-09-05T13:57:21.812Z")

{ "_id" : 10001, "count" : 1, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:40:58.034Z") }

{ "_id" : 10002, "count" : 2, "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:41:57.860Z") }

{ "_id" : 10003, "count" : 3, "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:42:09.794Z") }

{ "_id" : 10004, "count" : 4, "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:42:19.185Z") }

{ "_id" : 10005, "count" : 5, "news" : "new a good day", "time" : ISODate("2011-09-05T13:42:36.860Z") }

> db.news.find({"count":{"$gt":2,"$lte":4}},{"_id":0,"time":1,"news":1}) // select time,news from [news] where count>2 and count<=4

{ "news" : "i hava a dream", "time" : ISODate("2011-09-05T13:42:09.794Z") }

{ "news" : "wow! it is very good!", "time" : ISODate("2011-09-05T13:42:19.185Z") }

下面是对应的C#代码

FindAllAs<TDocument>()是一个泛型方法，可以用原生态BsonDocument和自定义类型News作为类型参数。MongoCursor<TDocument> FindAs<TDocument>(IMongoQuery query) 泛型查找，MongoCursor FindAs(Type, IMongoQuery)指定Type类型，并且两个方法都返回游标。而且MongoDB也提供Linq的查询操作。

 1     public class News
 2     {
 3         public int _id { get; set; }
 4         public int count { get; set; }
 5         public string news { get; set; }
 6         public DateTime time { get; set; }
 7     }
 8 
 9 MongoCursor<BsonDocument> allDoc = coll.FindAllAs<BsonDocument>();
10 BsonDocument doc = allDoc.First(); //BsonDocument类型参数
11 
12 MongoCursor<News> allNews = coll.FindAllAs<News>();
13 News aNew = allNews.First(); //News类型参数
14 
15 News firstNews = coll.FindOneAs<News>(); //查找第一个文档
16 
17 QueryDocument query = new QueryDocument(); //定义查询文档
18 query.Add("_id", 10001);
19 query.Add("count", 1);
20 MongoCursor<News> qNews = coll.FindAs<News>(query);
21 
22 
23 BsonDocument bd = new BsonDocument();//定义查询文档 count>2 and count<=4
24 bd.Add("$gt", 2);
25 bd.Add("$lte", 4);
26 QueryDocument query_a = new QueryDocument();
27 query_a.Add("count",bd);
28 
29 FieldsDocument fd = new FieldsDocument();
30 fd.Add("_id", 0);
31 fd.Add("count", 1);
32 fd.Add("time", 1);
33 
34 MongoCursor<News> mNewss = coll.FindAs<News>(query_a).SetFields(fd);//只返回count和time
35 
36 var time = BsonDateTime.Create("2011/9/5 23:26:00");
37 BsonDocument db_t = new BsonDocument();
38 db_t.Add("$gt", time);
39 QueryDocument qd_3 = new QueryDocument();
40 qd_3.Add("time", db_t);
41 
42 MongoCursor<News> mNews = coll.FindAs<News>(qd_3);//

如果要看更多，请访问我之前的MongoDb系列文章

作者: Yoolo

出处：http://www.cnblogs.com/yoolonet/archive/2011/09/06/2168447.html

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