2.非关系型数据库（Nosql）之mongodb：mongodb显示所有数据库，使用数据库，集合创建（显示和隐式创建），集合查询，初步数据的增删改查,分页

1代开一个cmd窗口，当作mongodb客户端，执行以下命令：

mongo localhost:27017

2查看所有的数据库：

> show dbs;

admin (empty)

local 0.078GB

3 db命令，查看当前窗口在那个数据库下面（test数据库没有任何数据，在内存里面）：

4创建集合

A 显示创建

db.createCollection(“collectionName”);

> db.createCollection("c1")

{ "ok" : 1 }

B 隐式创建

> db.c2.insert({name:"zhangsan",age:31})

WriteResult({ "nInserted" : 1 });

显示集合

show collections;

5 CRUD

A添加

db.collectionName.insert({})

> db.c2.insert({name:"zhangsan",age:31})

WriteResult({ "nInserted" : 1 })

> show collections;

system.indexes

> var i = 1+2;

> i

> for(var i = 1 ; i <= 10000;i++){

... db.c1.insert({name:'toto',age:24})

... }

WriteResult({ "nInserted" : 1 })

清屏命令：cls

B删除

db.collectionName.remove();

> db.c4.insert({name:"zhangsan",age:20});

WriteResult({ "nInserted" : 1 })

> db.c4.insert({name:"lisi",age:24});

WriteResult({ "nInserted" : 1 })

db.c4.find();

> db.c4.remove({name:"zhangsan"});

WriteResult({ "nRemoved" : 1 })

> db.c4.find();

{ "_id" : ObjectId("543e0b6ae2c90313035e7ce3"), "name" : "lisi", "age" : 24 }

C查询

A db.collectionName.find({条件});

eg：db.c3.find();

再如：

> db.c4.find({name:"lisi"});

{ "_id" : ObjectId("543e0b6ae2c90313035e7ce3"), "name" : "lisi", "age" : 24 }

B查找集合中的第一条数据

db.collectionName.findOne();

eg：

> db.c4.find();

{ "_id" : ObjectId("543e0b6ae2c90313035e7ce3"), "name" : "lisi", "age" : 24 }

{ "_id" : ObjectId("543e0d96e2c90313035e7ce4"), "name" : "wangwu", "age" : 20 }

{ "_id" : ObjectId("543e0da0e2c90313035e7ce5"), "name" : "zhaoliu", "age" : 25 }

{ "_id" : ObjectId("543e0da8e2c90313035e7ce6"), "name" : "tianqi", "age" : 25 }

> db.c4.findOne();

{

"_id" : ObjectId("543e0b6ae2c90313035e7ce3"),

"name" : "lisi",

"age" : 24

}

注意：_id每个表都有，是mongodb自动维护的。

C查询集合中的文档，返回某些特定的键值

除了查询表达式以外，Mongodb还支持一些额外的参数选项，例如，我们可能仅仅只想返回某些特定的字段值：

> db.c4.find({name:"wangwu"},{name:1});

{ "_id" : ObjectId("543e0d96e2c90313035e7ce4"), "name" : "wangwu" }

D查询显示问题

> for(var i = 1; i<=30;i++){

... db.c4.insert({name:"tuzuoquan",age:i});

... }

WriteResult({ "nInserted" : 1 })

查询：

> db.c4.find();

{ "_id" : ObjectId("543e0b6ae2c90313035e7ce3"), "name" : "lisi", "age" : 24 }

{ "_id" : ObjectId("543e0d96e2c90313035e7ce4"), "name" : "wangwu", "age" : 20 }

{ "_id" : ObjectId("543e0da0e2c90313035e7ce5"), "name" : "zhaoliu", "age" : 25 }

{ "_id" : ObjectId("543e0da8e2c90313035e7ce6"), "name" : "tianqi", "age" : 25 }

{ "_id" : ObjectId("543e104fe2c90313035e7ce7"), "name" : "tuzuoquan", "age" : 1 }

{ "_id" : ObjectId("543e104fe2c90313035e7ce8"), "name" : "tuzuoquan", "age" : 2 }

{ "_id" : ObjectId("543e104fe2c90313035e7ce9"), "name" : "tuzuoquan", "age" : 3 }

{ "_id" : ObjectId("543e104fe2c90313035e7cea"), "name" : "tuzuoquan", "age" : 4 }

{ "_id" : ObjectId("543e104fe2c90313035e7ceb"), "name" : "tuzuoquan", "age" : 5 }

{ "_id" : ObjectId("543e104fe2c90313035e7cec"), "name" : "tuzuoquan", "age" : 6 }

{ "_id" : ObjectId("543e104fe2c90313035e7ced"), "name" : "tuzuoquan", "age" : 7 }

{ "_id" : ObjectId("543e104fe2c90313035e7cee"), "name" : "tuzuoquan", "age" : 8 }

{ "_id" : ObjectId("543e104fe2c90313035e7cef"), "name" : "tuzuoquan", "age" : 9 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf0"), "name" : "tuzuoquan", "age" : 10 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf1"), "name" : "tuzuoquan", "age" : 11 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf2"), "name" : "tuzuoquan", "age" : 12 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf3"), "name" : "tuzuoquan", "age" : 13 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf4"), "name" : "tuzuoquan", "age" : 14 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf5"), "name" : "tuzuoquan", "age" : 15 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf6"), "name" : "tuzuoquan", "age" : 16 }

Type "it" for more

> it

{ "_id" : ObjectId("543e104fe2c90313035e7cf7"), "name" : "tuzuoquan", "age" : 17 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf8"), "name" : "tuzuoquan", "age" : 18 }

{ "_id" : ObjectId("543e104fe2c90313035e7cf9"), "name" : "tuzuoquan", "age" : 19 }

{ "_id" : ObjectId("543e104fe2c90313035e7cfa"), "name" : "tuzuoquan", "age" : 20 }

{ "_id" : ObjectId("543e104fe2c90313035e7cfb"), "name" : "tuzuoquan", "age" : 21 }

{ "_id" : ObjectId("543e104fe2c90313035e7cfc"), "name" : "tuzuoquan", "age" : 22 }

{ "_id" : ObjectId("543e104fe2c90313035e7cfd"), "name" : "tuzuoquan", "age" : 23 }

{ "_id" : ObjectId("543e104fe2c90313035e7cfe"), "name" : "tuzuoquan", "age" : 24 }

{ "_id" : ObjectId("543e104fe2c90313035e7cff"), "name" : "tuzuoquan", "age" : 25 }

{ "_id" : ObjectId("543e104fe2c90313035e7d00"), "name" : "tuzuoquan", "age" : 26 }

{ "_id" : ObjectId("543e104fe2c90313035e7d01"), "name" : "tuzuoquan", "age" : 27 }

{ "_id" : ObjectId("543e104fe2c90313035e7d02"), "name" : "tuzuoquan", "age" : 28 }

{ "_id" : ObjectId("543e104fe2c90313035e7d03"), "name" : "tuzuoquan", "age" : 29 }

{ "_id" : ObjectId("543e104fe2c90313035e7d04"), "name" : "tuzuoquan", "age" : 30 }

> db.c4.count();

>总结：

Mongodb客户端默认一次显示20条记录

Eg:显示age大于20个数据：

> db.c4.find({age:{$gt:20}});