> show dbs 
local  0.000GB
myblog 0.000GB

> use myblog
switched to db myblog

> show collections
articles
replicationColletion
sessions
users
wangduanduan

// 在已经存在的集合中插入数据
> db.users.insert({name:'hh',age:23})
Inserted 1 record(s) in 43ms

// 在不存在的集合中插入数据,集合不存在则自动创建集合并插入
> db.students.insert({name:'hh',age:23})
Inserted 1 record(s) in 72ms

> db.users.find()
/* 1 */
{
  "_id" : ObjectId("583e908453be942d0c5419dc"),
  "login_name" : "wangduanduan",
  "password" : "wrong age"
}

/* 2 */
{
  "_id" : ObjectId("583ed2a5cc9a937db049616d"),
  "login_name" : "hh",
  "password" : "sdfsdf"
}

/* 3 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

/* 4 */
{
  "_id" : ObjectId("583fb707b12f8b7a7aa37573"),
  "name" : "hh",
  "age" : 23.0
}

> db.users.find({name:'wangduanduan'})
/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

// 这是错的，查不到结果
> db.users.find({_id:'583fb2e9b12f8b7a7aa37572'})
Fetched 0 record(s) in 1ms

// 这是正确的
> db.users.find({_id:ObjectId('583fb2e9b12f8b7a7aa37572')})
/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

> db.users.count()
4

// 查询用户里年龄大于30岁的人， 其他条件以此类推
> db.user.find({age:{$gt:30}})

/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

// 查询名字是wangduanduan,age=34的用户
> db.users.find({name:'wangduanduan',age:34})
/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

// 查询名字是wangduanduan,或hh的用户
> db.users.find({name:{$in:['wangduanduan','hh']}})
/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

// 查询名字不是wangduanduan或者hh的用户
> db.users.find({name:{$nin:['wangduanduan','hh']}})
/* 1 */
{
  "_id" : ObjectId("583e908453be942d0c5419dc"),
  "login_name" : "wangduanduan",
  "password" : "wrong age"
}

/* 2 */
{
  "_id" : ObjectId("583ed2a5cc9a937db049616d"),
  "login_name" : "hh",
  "password" : "sdfsdf"
}

// 查询名字是中含有duan的用户
> db.users.find({name:/duan/})
/* 1 */
{
  "_id" : ObjectId("583fb2e9b12f8b7a7aa37572"),
  "name" : "wangduanduan",
  "age" : 34.0
}

/* 2 */
{
  "_id" : ObjectId("583fc919b12f8b7a7aa37575"),
  "name" : "wangduanduan",
  "age" : 45.0
}

// 返回含有login_name字段的文档
db.getCollection('users').find({$where:function(){
  return !!this.login_name;
}})