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);
//
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
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接.
转载于:https://www.cnblogs.com/yoolonet/archive/2011/09/06/2168447.html
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