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。
MongoDB Find查询
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); //
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
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