MongoDB是一个Nosql数据库系统，其提供了DBMS的基本功能和行为。
MongoDB命令帮助系统
>help
db.help() help on db methods
db.mycoll.help() help on collection methods
sh.help() sharding helpers
rs.help() replica set helpers
help admin administrative help
help connect connecting to a db help
help keys key shortcuts
help misc misc things to know
help mr mapreduce
show dbs show database names
show collections show collections in current database
show users show users in current database
show profile show most recent system.profile entries with time >= 1ms
show logs show the accessible logger names
show log [name] prints out the last segment of log in memory, 'global' is default
use <db_name> set current database
db.foo.find() list objects in collection foo
db.foo.find( { a : 1 } ) list objects in foo where a == 1
it result of the last line evaluated; use to further iterate
DBQuery.shellBatchSize = x set default number of items to display on shell
exit quit the mongo shell
通过客户端连接MongoDB服务器,执行help命令。这是MongoDB最顶层的命令列表，主要告诉我们管理数据库相关的一些抽象的范畴：数据库操作帮助、集合操作帮助、replica set帮助等，比如你想了解数据库操作更详细的帮助命令，可以直接使用db.help()，如下所示：
>db.help()
DB methods:
db.adminCommand(nameOrDocument) - switches to 'admin' db, and runs command [ just calls db.runCommand(...) ]
db.auth(username, password)
db.cloneDatabase(fromhost)
db.commandHelp(name) returns the help for the command
db.copyDatabase(fromdb, todb, fromhost)
db.createCollection(name, { size : ..., capped : ..., max : ... } )
db.createUser(userDocument)
db.currentOp() displays currently executing operations in the db
db.dropDatabase()
db.eval() - deprecated
db.fsyncLock() flush data to disk and lock server for backups
db.fsyncUnlock() unlocks server following a db.fsyncLock()
db.getCollection(cname) same as db['cname'] or db.cname
db.getCollectionInfos([filter]) - returns a list that contains the names and options of the db's collections
db.getCollectionNames()
db.getLastError() - just returns the err msg string
db.getLastErrorObj() - return full status object
db.getLogComponents()
db.getMongo() get the server connection object
db.getMongo().setSlaveOk() allow queries on a replication slave server
db.getName()
db.getPrevError()
db.getProfilingLevel() - deprecated
db.getProfilingStatus() - returns if profiling is on and slow threshold
db.getReplicationInfo()
db.getSiblingDB(name) get the db at the same server as this one
db.getWriteConcern() - returns the write concern used for any operations on this db, inherited from server object if set
db.hostInfo() get details about the server's host
db.isMaster() check replica primary status
db.killOp(opid) kills the current operation in the db
db.listCommands() lists all the db commands
db.loadServerScripts() loads all the scripts in db.system.js
db.logout()
db.printCollectionStats()
db.printReplicationInfo()
db.printShardingStatus()
db.printSlaveReplicationInfo()
db.dropUser(username)
db.repairDatabase()
db.resetError()
db.runCommand(cmdObj) run a database command. if cmdObj is a string, turns it into { cmdObj : 1 }
db.serverStatus()
db.setLogLevel(level,)
db.setProfilingLevel(level,) 0=off 1=slow 2=all
db.setWriteConcern( ) - sets the write concern for writes to the db
db.unsetWriteConcern( ) - unsets the write concern for writes to the db
db.setVerboseShell(flag) display extra information in shell output
db.shutdownServer()
db.stats()
db.version() current version of the server
它会列出数据库操作方法。又比如你想查询对数据库集合的操作方法。使用db.mycoll.help()
> db.mycoll.help()
DBCollection help
db.mycoll.find().help() - show DBCursor help
db.mycoll.bulkWrite( operations, <optional params> ) - bulk execute write operations, optional parameters are: w, wtimeout, j
db.mycoll.count( query = {}, <optional params> ) - count the number of documents that matches the query, optional parameters are: limit, skip, hint, maxTimeMS
db.mycoll.copyTo(newColl) - duplicates collection by copying all documents to newColl; no indexes are copied.
db.mycoll.convertToCapped(maxBytes) - calls {convertToCapped:'mycoll', size:maxBytes}} command
db.mycoll.createIndex(keypattern[,options])
db.mycoll.createIndexes([keypatterns], <options>)
db.mycoll.dataSize()
db.mycoll.deleteOne( filter, <optional params> ) - delete first matching document, optional parameters are: w, wtimeout, j
db.mycoll.deleteMany( filter, <optional params> ) - delete all matching documents, optional parameters are: w, wtimeout, j
db.mycoll.distinct( key, query, <optional params> ) - e.g. db.mycoll.distinct( 'x' ), optional parameters are: maxTimeMS
db.mycoll.drop() drop the collection
db.mycoll.dropIndex(index) - e.g. db.mycoll.dropIndex( "indexName" ) or db.mycoll.dropIndex( { "indexKey" : 1 } )
db.mycoll.dropIndexes()
db.mycoll.ensureIndex(keypattern[,options]) - DEPRECATED, use createIndex() instead
db.mycoll.explain().help() - show explain help
db.mycoll.reIndex()
db.mycoll.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.
e.g. db.mycoll.find( {x:77} , {name:1, x:1} )
db.mycoll.find(...).count()
db.mycoll.find(...).limit(n)
db.mycoll.find(...).skip(n)
db.mycoll.find(...).sort(...)
db.mycoll.findOne([query], [fields], [options], [readConcern])
db.mycoll.findOneAndDelete( filter, <optional params> ) - delete first matching document, optional parameters are: projection, sort, maxTimeMS
db.mycoll.findOneAndReplace( filter, replacement, <optional params> ) - replace first matching document, optional parameters are: projection, sort, maxTimeMS, upsert, returnNewDocument
db.mycoll.findOneAndUpdate( filter, update, <optional params> ) - update first matching document, optional parameters are: projection, sort, maxTimeMS, upsert, returnNewDocument
db.mycoll.getDB() get DB object associated with collection
db.mycoll.getPlanCache() get query plan cache associated with collection
db.mycoll.getIndexes()
db.mycoll.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
db.mycoll.insert(obj)
db.mycoll.insertOne( obj, <optional params> ) - insert a document, optional parameters are: w, wtimeout, j
db.mycoll.insertMany( [objects], <optional params> ) - insert multiple documents, optional parameters are: w, wtimeout, j
db.mycoll.mapReduce( mapFunction , reduceFunction , <optional params> )
db.mycoll.aggregate( [pipeline], <optional params> ) - performs an aggregation on a collection; returns a cursor
db.mycoll.remove(query)
db.mycoll.replaceOne( filter, replacement, <optional params> ) - replace the first matching document, optional parameters are: upsert, w, wtimeout, j
db.mycoll.renameCollection( newName , <dropTarget> ) renames the collection.
db.mycoll.runCommand( name , <options> ) runs a db command with the given name where the first param is the collection name
db.mycoll.save(obj)
db.mycoll.stats({scale: N, indexDetails: true/false, indexDetailsKey: <index key>, indexDetailsName: <index name>})
db.mycoll.storageSize() - includes free space allocated to this collection
db.mycoll.totalIndexSize() - size in bytes of all the indexes
db.mycoll.totalSize() - storage allocated for all data and indexes
db.mycoll.update( query, object[, upsert_bool, multi_bool] ) - instead of two flags, you can pass an object with fields: upsert, multi
db.mycoll.updateOne( filter, update, <optional params> ) - update the first matching document, optional parameters are: upsert, w, wtimeout, j
db.mycoll.updateMany( filter, update, <optional params> ) - update all matching documents, optional parameters are: upsert, w, wtimeout, j
db.mycoll.validate( <full> ) - SLOW
db.mycoll.getShardVersion() - only for use with sharding
db.mycoll.getShardDistribution() - prints statistics about data distribution in the cluster
db.mycoll.getSplitKeysForChunks( <maxChunkSize> ) - calculates split points over all chunks and returns splitter function
db.mycoll.getWriteConcern() - returns the write concern used for any operations on this collection, inherited from server/db if set
db.mycoll.setWriteConcern( <write concern doc> ) - sets the write concern for writes to the collection
db.mycoll.unsetWriteConcern( <write concern doc> ) - unsets the write concern for writes to the collection
基本命令
1、show dbs
显示当前数据库服务器上的数据库
2、use test
切换到指定数据库test的上下文，可以在此上下文中管理test数据库以及其中的集合等
3、show collections
显示数据库中所有的集合（collection）
4、db.serverStatus()
查看数据库服务器的状态。
5、db.stats()
查询指定数据库统计信息
6、db.getCollectionNames()
查询指定数据库包含的集合名称列表
7、db.shutdownServer()
终止服务器进程。
DDL和DML
1、 use test
创建数据库
2、db.dropDatabase()
删除数据库。先使用use test切换到test数据库，使用db.dropDatabase()即可删除数据库。
3、db.createCollection(name, { size : ..., capped : ..., max : ... } )
创建集合
4、db.mycoll.drop()
删除集合
5、db.mycoll.save({'version':'3.5', 'segment':'e3ol6'})
插入更新记录。
6、db.mycoll.findOne({'version':'3.5'})
查询一条记录。
7、db.mycoll.find({'version':'3.5'})
查询多条记录。
8、db.mycoll.remove({'version':'3.5'})
删除记录。
9、db.mycoll.ensureIndex({'title':1, 'url':-1})
创建索引
可以使用集合的ensureIndex(keypattern[,options])方法，上述，ensureIndex方法参数中，数字1表示升序，-1表示降序。
10、 db.mycoll.dropIndex(name)
删除索引。
11、db.mycoll.count()
统计集合记录数。
12、db.mycoll.find().count()
查询并统计结果记录数。
find()可以提供查询参数，然后查询并统计结果。
13、db.mycoll.storageSize()
查询指定数据库的集合当前可用的存储空间。
14、db.baseSe.totalSize()
查询指定数据库的集合分配的存储空间。
备份恢复
待续。。。