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()
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,<component>)
db.setProfilingLevel(level,<slowms>) 0=off 1=slow 2=all
db.setWriteConcern( <write concern doc> ) - sets the write concern for writes to the db
db.unsetWriteConcern( <write concern doc> ) - 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
对数据库进行管理和操作的基本命令，可以从上面获取到。如果想要得到更多，而且每个命令的详细用法，可以使用上面列出的db.listCommands()查询。
另一个比较基础的是对指定数据库的集合进行操作、管理和监控，可以通过查询db.mycoll.help()获取到：
db.mycoll.help()
DBCollection help
db.mycoll.find().help() - show DBCursor help
db.mycoll.count()
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.dataSize()
db.mycoll.distinct( key ) - e.g. db.mycoll.distinct( 'x' )
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])
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])
db.mycoll.findAndModify( { update : ... , remove : bool [, query: {}, sort: {}, 'new': false] } )
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.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.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.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
有关数据库和集合管理的相关命令，是最基础和最常用的，如集合查询、索引操作等。下面通过实际的例子来演示一些常见的命令：
一、基本命令
1）show dbs
显示当前数据库服务器上的数据库
2）use pagedb
切换到指定数据库pagedb的上下文，可以在此上下文中管理pagedb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）