这次继续看mongodb中的分页。首先依然是插入数据： 

1）
db.Blog.insert( { name : "Denis", age : 20, city : "Princeton" } )
db.Blog.insert( { name : "Abe", age : 30, city : "Amsterdam" } )
db.Blog.insert( { name : "John", age : 40, city : "New York" } )
db.Blog.insert( { name : "Xavier", age : 10, city : "Barcelona" } )
db.Blog.insert( { name : "Zen", age : 50, city : "Kyoto" } )
2) 查询下
db.Blog.find()
结果为：
{ "_id" : ObjectId("51028ae0a8c33b71ed76a807"), "name" : "Denis", "age" : 20, "city" : "Princeton" }
{ "_id" : ObjectId("51028ae0a8c33b71ed76a808"), "name" : "Abe", "age" : 30, "city" : "Amsterdam" }
{ "_id" : ObjectId("51028ae2a8c33b71ed76a809"), "name" : "John", "age" : 40, "city" : "New York" }
{ "_id" : ObjectId("51028ae2a8c33b71ed76a80a"), "name" : "Xavier", "age" : 10, "city" : "Barcelona" }
{ "_id" : ObjectId("51028ae4a8c33b71ed76a80b"), "name" : "Zen", "age" : 50, "city" : "Kyoto" }
3）每次只显示2条，使用limit就可以了
db.Blog.find().limit(2)
结果：
{ "_id" : ObjectId("5103e22c88a39c3c0b2585e1"), "name" : "Denis", "age" : 20, "city" : "Princeton" }
{ "_id" : ObjectId("5103e22d88a39c3c0b2585e2"), "name" : "Abe", "age" : 30, "city" : "Amsterdam" }
需要排下序，没问题，加上sort就可以了
，比如根据name排序
db.Blog.find().sort({name: 1}).limit(2)
{ "_id" : ObjectId("5103e22d88a39c3c0b2585e2"), "name" : "Abe", "age" : 30, "city" : "Amsterdam" }
{ "_id" : ObjectId("5103e22c88a39c3c0b2585e1"), "name" : "Denis", "age" : 20, "city" : "Princeton" }
如果只需要显示某些列，可以这样：
db.Blog.find(null, {name: 1, _id: 0}).sort({name: 1}).limit(2)
_id:0这样的方式，连id列也不显示了
只显示
{ "name" : "Abe" }
{ "name" : "Denis" }
3 分页
比如要范围第3，第4条记录，使用skip(2)，跳过2条
db.Blog.find(null, {name: 1, _id: 0}).sort({name: 1}).limit(2).skip(2)
结果为：
{ "name" : "John" }
{ "name" : "Xavier" }
如果skip的数超过记录条数，也是不会报错的了：
比如：
db.Blog.find(null, {name: 1, _id: 0}).sort({name: 1}).limit(2).skip(6)
另外，使用$natural参数可以倒过来输出所有记录，比如：
db.Blog.find().sort( { $natural: -1 } )
{ "_id" : ObjectId("5103eaa688a39c3c0b2585ed"), "name" : "Zen", "age" : 50, "city" : "Kyoto" }
{ "_id" : ObjectId("5103eaa588a39c3c0b2585ec"), "name" : "Xavier", "age" : 10, "city" : "Barcelona" }
{ "_id" : ObjectId("5103eaa588a39c3c0b2585eb"), "name" : "John", "age" : 40, "city" : "New York" }
{ "_id" : ObjectId("5103eaa588a39c3c0b2585ea"), "name" : "Abe", "age" : 30, "city" : "Amsterdam" }
{ "_id" : ObjectId("5103eaa588a39c3c0b2585e9"), "name" : "Denis", "age" : 20, "city" : "Princeton" }
要注意的是，居然说超过32MB 会报错，说要用 cursor.limit()或者在要排序的列中创建索引，才不报错？