mongoDB操作命令，摘自官方helper

help                         show help
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
use <db name>                set curent database to <db name>

db.addUser (username, password)
db.removeUser(username)

db.cloneDatabase(fromhost)
db.copyDatabase(fromdb, todb, fromhost)
db.createCollection(name, { size : ..., capped : ..., max : ... } )

db.getName()
db.dropDatabase()

// runs the collstats] command on each collection in the database
db.printCollectionStats()

db.currentOp() displays the current operation in the db
db.killOp() kills the current operation in the db

db.getProfilingLevel()
db.setProfilingLevel(level) 0=off 1=slow 2=all

db.getReplicationInfo()
db.printReplicationInfo()
db.printSlaveReplicationInfo()
db.repairDatabase()

db.version() current version of the server

db.shutdownServer()

db.foo.drop() drop the collection
db.foo.dropIndex(name)
db.foo.dropIndexes()
db.foo.getIndexes()
db.foo.ensureIndex(keypattern,options) - options object has these possible
fields: name, unique, dropDups

db.foo.find( [query] , [fields]) - first parameter is an optional
query filter. second parameter
is optional
set of fields to return.
e.g. db.foo.find(
{ x : 77 } ,
{ name : 1 , x : 1 } )
db.foo.find(...).count()
db.foo.find(...).limit(n)
db.foo.find(...).skip(n)
db.foo.find(...).sort(...)
db.foo.findOne([query])

db.foo.getDB() get DB object associated with collection

db.foo.count()
db.foo.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )

db.foo.renameCollection( newName ) renames the collection

db.foo.stats()
db.foo.dataSize()
db.foo.storageSize() - includes free space allocated to this collection
db.foo.totalIndexSize() - size in bytes of all the indexes
db.foo.totalSize() - storage allocated for all data and indexes
db.foo.validate() (slow)

db.foo.insert(obj)
db.foo.update(query, object[, upsert_bool])
db.foo.save(obj)
db.foo.remove(query) - remove objects matching query
remove({}) will remove all