MongoDB 学习笔记（一）
1.安装 ，安装好弄，到官网下载下来 解压开来 就欧啦。下载地址在这里：下载地址
还有一些入门的概念
row in a relational database management system (but much more expressive).
文档是mongoDB的基本数据单元，和关系型数据库的一行数据一样，但是更灵活我感觉。
比如一个document可以存储{ "_id" : { "$oid" : "53abe1ab18713765b33f2738"} , "usrname" : "mongo" , "friends" : 32.0 , "enemies" : 2.0}
• Similarly, a collection can be thought of as a table with a dynamic schema.
同样的一个colletion是啥呢 就是一个和关系型数据库的表类似，但是是动态模式（有道翻译我不是打广告）就是没有约束呗想怎么存就怎么存。
which can have its own collections.
一个示例可以支撑多个数据库，每个数据库又有自己的colletion，
每隔文档都已自己的一个特殊的“_id”,在一个集合里边是唯一的。
• MongoDB comes with a simple but powerful JavaScript shell, which is useful for
the administration of MongoDB instances and data manipulation.
MongoDB有一个javascript外壳，由管理员用来管理数据库实例，和数据操作。（翻译完毕，英文来自mongodb_the_definitive_guide_2nd_edition.pdf 这里有下载 打个小广告http://download.csdn.net/detail/u014133453/7557425）
The keys in a document are strings. Any UTF-8 character is allowed in a key, with a few
notable exceptions:
只要是UTF-8就行 ，但是要注意
• Keys must not contain the character \0 (the null character). This character is used
to signify the end of a key.
键不能有\0 这个字符标志着键的结束
• The . and $ characters have some special properties and should be used only in
certain circumstances In general, they should be
considered reserved, and drivers will complain if they are used inappropriately.
这个 . 和 $ 也不行，他俩有一些特殊的属性，只能用在特定的情况下，一般情况下认为这两哥们是被保留的司机就会抱怨如果用的不得当，显然不是这么翻译啊 如果用的不合适，驱动不一定会正常工作奥。
另外 mongodb 类型和大小写敏感
{"foo" : 3}
{"foo" : "3"} not same
{"foo" : 3}
{"Foo" : 3} not same too
另外啊 这个一个document 里边啊 不能有相同的key （书本写的就是严谨）
这就不行
{"greeting" : "Hello, world!", "greeting" : "Hello, MongoDB!"}
又另外 在document里 啊 键/值 是有顺序地 {"x" : 1, "y" : 2} {"y" : 2, "x" : 1} 是不一样地
这个顺序不是很重要，所以你在设计你的模式的时候不能靠特定的格式 即使是这样mongoDB 也会将它重组。
虽然说collection 在上述原则上可以放置任意document但是我们为什么需要多余一个的collection呢 书上的原话啊 我翻译下
• Keeping different kinds of documents in the same collection can be a nightmare
for developers and admins. Developers need to make sure that each query is only
returning documents of a certain type or that the application code performing a
query can handle documents of different shapes. If we’re querying for blog posts,
it’s a hassle to weed out documents containing author data.
如果你把不同类型的document放在同一个collection下这对管理员和开发者都是噩梦。开发人员要确保每次查询返回特定的类型或者说程序代码能够处理的了不同类型的document。比我们查询帖子，我们剔除了包含作者信息的document是困难的好蹩脚。
• It is much faster to get a list of collections than to extract a list of the types in a
collection. For example, if we had a "type" field in each document that specified
whether the document was a “skim,” “whole,” or “chunky monkey,” it would be much
slower to find those three values in a single collection than to have three separate
collections and query the correct collection.
• Grouping documents of the same kind together in the same collection allows for
data locality. Getting several blog posts from a collection containing only posts will
likely require fewer disk seeks than getting the same posts from a collection con‐
taining posts and author data.
• We begin to impose some structure on our documents when we create indexes.
(This is especially true in the case of unique indexes.) These indexes are defined per
collection. By putting only documents of a single type into the same collection, we
can index our collections more efficiently.
又来了一些限制 ，collection的名字不能是空字符串，不能是\0 , 不能已system开头，为的是mongodb内部的collection
特别注意不能包含$字符
另外 子集合的概念
Subcollections are a great way to organize data in MongoDB, and their use is highly
recommended.
数据库的名字里不能包含这个
不能为空 /, \, ., ", *, <, >, :, |, ?, $, (a
single space), or \0 (the null character) 基本来书字母数字就行啦 小写 最长64字节 为什么呢包不准他数据库名会成为你文件名这就是为什么他又这么多限制
2.运行 在/bin 目录下有个mongod命令 先看看有什吗参数再说
-h [ --help ] show this usage information
--version show version information
-f [ --config ] arg configuration file specifying additional options
-v [ --verbose ] [=arg(=v)] be more verbose (include multiple times for more
verbosity e.g. -vvvvv)
--quiet quieter output
--port arg specify port number - 27017 by default
--bind_ip arg comma separated list of ip addresses to listen on
- all local ips by default
--maxConns arg max number of simultaneous connections - 1000000
by default
--logpath arg log file to send write to instead of stdout - has
to be a file, not directory
--syslog log to system's syslog facility instead of file
or stdout
--syslogFacility arg syslog facility used for monogdb syslog message
--logappend append to logpath instead of over-writing
--timeStampFormat arg Desired format for timestamps in log messages.
One of ctime, iso8601-utc or iso8601-local
--pidfilepath arg full path to pidfile (if not set, no pidfile is
created)
--keyFile arg private key for cluster authentication
--setParameter arg Set a configurable parameter
--httpinterface enable http interface
--clusterAuthMode arg Authentication mode used for cluster
authentication. Alternatives are
(keyFile|sendKeyFile|sendX509|x509)
--nounixsocket disable listening on unix sockets
--unixSocketPrefix arg alternative directory for UNIX domain sockets
(defaults to /tmp)
--fork fork server process
--auth run with security
--noauth run without security
--ipv6 enable IPv6 support (disabled by default)
--jsonp allow JSONP access via http (has security
implications)
--rest turn on simple rest api
--slowms arg (=100) value of slow for profile and console log
--profile arg 0=off 1=slow, 2=all
--cpu periodically show cpu and iowait utilization
--sysinfo print some diagnostic system information
--dbpath arg (=/data/db) directory for datafiles - defaults to /data/db/
--directoryperdb each database will be stored in a separate
directory
--noIndexBuildRetry don't retry any index builds that were
interrupted by shutdown
--noprealloc disable data file preallocation - will often hurt
performance
--nssize arg (=16) .ns file size (in MB) for new databases
--quota limits each database to a certain number of files
(8 default)
--quotaFiles arg number of files allowed per db, implies --quota
--smallfiles use a smaller default file size
--syncdelay arg (=60) seconds between disk syncs (0=never, but not
recommended)
--upgrade upgrade db if needed
--repair run repair on all dbs
--repairpath arg root directory for repair files - defaults to
dbpath
--noscripting disable scripting engine
--notablescan do not allow table scans
--journal enable journaling
--nojournal disable journaling (journaling is on by default
for 64 bit)
--journalOptions arg journal diagnostic options
--journalCommitInterval arg how often to group/batch commit (ms)
--shutdown kill a running server (for init scripts)
Replication options:
--oplogSize arg size to use (in MB) for replication op log. default is
5% of disk space (i.e. large is good)
Master/slave options (old; use replica sets instead):
--master master mode
--slave slave mode
--source arg when slave: specify master as
--only arg when slave: specify a single database to replicate
--slavedelay arg specify delay (in seconds) to be used when applying
master ops to slave
--autoresync automatically resync if slave data is stale
Replica set options:
--replSet arg arg is
--replIndexPrefetch arg specify index prefetching behavior (if secondary)
[none|_id_only|all]
Sharding options: ERROR: dbpath (/data/db) does not exist.
--configsvr declare this is a config db of a cluster; default port
27019; default dir /data/configdbERROR: dbpath (/data/db) does not exist.
--shardsvr declare this is a shard db of a cluster; default port
27018
看着有点乱 先讲究看吧 ^ _ ^
怎么启动呢 ，在启动时 有个参数叫 --dbpath 这个是指定数据文件的路径 你要是不指定呢，结果是这样的 ERROR: dbpath (/data/db) does not exist. Create this directory or give existing directory in --dbp ，还是乖乖的指定吧，第一次启动比较慢 大家耐心等待就好啦。来个java喝喝。启动起来怎么关呢？mongod --shutdwon 这个参数一般情况下不行，它还是取找默认目录 There doesn't seem to be a server running with dbpath: /data/db ，所以你关数据库的时候也必须加上那个路径参数。这样你就可以把它关掉啦。
另外加上 --rest 网页才可以通过28017访问控制台。
2， mongoDB 里边有个默认的数据库test，里边有个默认的集合叫 foo.
当我们想插入一条数据时，这样就可已啦
首先运行 mongo 如后会出来一个shell 环境，你输入命令就行了。什么不知到有什么命令 help一下再说。
db.foo.insert({"usrname":"foo","userage":27})
WriteResult({ "nInserted" : 1 }) 这样你就成功插入了一条数据。
db.foo.findOne({{"usrname":"foo"}} 如果有多条匹配结果的话，他只会显示第一条～_~。