摘要:MongoDB 指令研究
儲存資料
	db.inboxs.save({inbox_id:"tomlai",tags:["tom","lai"]})
	查詢
	db.inboxs.find()
	db.inboxs.find({inbox_id:"tomlai"})
	陣列 OR 查詢
	db.inboxs.find({tags:{"$in":["lai"]}})
	陣列AND查詢
	db.inboxs.find({tags:{"$all":["lai"]}})
	大於小於查詢
	db.inboxs.find({age:{"$lt":30,"$gt":20}})
	存在查詢
	db.posts.find(tags:{$exists:true})
	Regular expressions
	db.posts.find({author:/^r*/i})
	Counting
	db.posts.find({author:"tomlai"}).count()
	update , add new comment 
	db.posts.update({i_d:"....",new_info}
	new_info{"$push":{comments:new_,comment},"$inc":{comments_count:1}}
	設定索引
	db.posts.ensureIndex({"comments.author":1})
	階層式查詢 
	db.posts.find({comments.author:"tomlai"})
	遞減排序兼取前五個
	db.posts.find().sort({date:-1}).limit(5)     
	db.jobs.findAndModify({query:{},sort:{},update:{$set:{}},new:true})