midunion虚拟货币
Ⅰ 你知道有哪些虚拟币呢
虚拟货币有哪些
现在比特币已经成为最著名的虚拟货币。比特币虚拟货币是通过复杂的计算而得到的货币。由于其算法的限制，其总量是有2100万个，而目前的开采量已超过1100万个。比特币已引起了Western Union、MoneyGram和PayPal等公司的关注。有消息称这些服务正在评估是否允许用户在各自平台上使用比特币。
亚马逊Coins
亚马逊是少数几家自主开发虚拟货币的大型科技公司。大部分情况下，这些公司的虚拟货币只能在各自网站上使用。亚马逊于5月份刚刚推出亚马逊Coins服务，目前可用于在Kindle Fire平台，以及应用商店和网站上购买游戏、应用和其他数字内容。1美元可购买100个亚马逊Coins，而大量购买将获得折扣，例如1000个亚马逊Coins售价为9.5美元
Ⅱ SQL嵌套查询完成外连接功能的改写
select name,title from actor,movies,actor_role where actor.AID=actor_role.AID and movies.MID=actor_role.MID
union all
select name, NULL title from actor b where not exists (select 1 from actor_role a where a.AID=b.AID)
出演过的
union all
没出演过的
Ⅲ ETB区块链技术
Economic International Technology简称ETB,中文名全球比特联盟， 为解决现在区块链技术所遇到的问题，2017年五月中旬由全球最大比特币矿工联盟发起成立ETB项目组，历时半年时间ETB通过最顶尖加密技术在继承比特币优良特性的基础上对现存问题进行革新，ETB加密货币总发行量2100万枚，ETB区块使用现在的线性算法进行挖矿动作，而是使用仿生的房产网络算力继承模式，形成一个虚拟货币房产网络，我们把每一个账户认定为一个ETB，把每一个支付结算应用利用房产末梢的模拟完成最终的支付即时完成。
伟大科技让原本复杂的世界变得简单了。久远的不必赘述，仅数十年来，计算机、互联网、智能手机等高新技术的纷至沓来，就让曾经普通人难以想象的事务，譬如全球通信变得现实且简单了。目前在更为复杂的全球房地产投融资领域，也正在迎来一场走向简单的变革。这得益于区块链技术的崛起和智能合约的运用，并由ETB平台带入了现实。
ETB希望，通过基于区块链技术和智能合约运用的投资平台，将全球投资者和房地产项目链接起来，并在线直观的呈现整个房地产项目的一切，从原材料、物流，施工到完工，再到经营和收益等等，让房地产投资变得透明、易懂、可预测，通过ETB平台，任何投资者都可以投资任何国家的房地产项目，地产商也将可以更直接的面对投资者。
不妨回忆一下我们的日常网购生活：当我们相中某款商品时，都会先将费用支付给交易平台，诸如淘宝或者京东，然后等待商家发货，在我们确认收到货物之后，平台再将费用转交给商家。在这个购物流程中，我们之所以能相信陌生的卖家，是因为我们别无选择的只能相信交易平台，否则就无法交易。而基于区块链技术就不必如此复杂了，比如在Eit平台，投资者和地产商只需要相信自己的判断就可以直接互动，Eit需要做的，只是对投资者身份和房地产项目进行严格审核，并提供代币保障平台交易的正常进行就可以了。
如果说昨天，区块链技术的应用还仅限于银行、证券、基金等少数金融领域，那么现在，区块链已经开始直接影响普通人的日常生活，ETB房地产投资分散型平台的出现，以及区块链进入建筑业，改变了我们对房地产投融资领域的传统看法，信任与合作已经如此简单。
比特币社区作为比特币技术的研发中心，同时担负起了引导整个行业技术革新的使命，我们在不断演进区块链技术的过程中发现，整个行业出现了一些致命的问题!包括比特币的区块链技术!所以我们从2018年起开始对现在的区块链技术进行革新和迭代，以下内容将详细的阐述区块链所遇到的问题以及Eit区块链怎么来解决这些问题，同时公布生命体区块链核心算法。
问题一：区块链无法真正融入消费场景!
比特币的长期愿景就是对现有货币体系进行数字化对接，让比特币成为现实货币的数字化内核，但是不管是比特币还是其他的区块链技术都无法真正实现这个目标，至少到现在为止所有的区块链都只具备一个属性那就是投资属性，出现这个问题的主要原因其实是技术上的几个问题，第一，数字货币的交易时间，现存的区块链交易技术是无法实现实时交易的，因为在设计之初为了安全和去中心化等问题，我们抛弃了大量时效性的方法。无法实时完成货币交割，这是最大的问题!
问题二：区块遗失!
这个问题是个综合的问题，部分区块的遗失一般出现在几种情况下：
1、账户标记遗失
2、矿机标记遗失
3、所有人无有效继承
这个问题看似很小，但是对于区块链的影响是致命的，因为经过不断的遗失最终区块的总量将会越来越少，所以对应的价值将会持续增高，增加的投机者的投资驱动力，对一个区块链的健康长期的发展产生恶性循环，并且让用户对整个区块链无法信任。
问题三：去中心化技术运营
比特币社区就是为了去中心化的技术更新而存在的，但是我们其实无法把真正好的技术更新快速完成因为大部分的冷钱包和矿机要接受这一次迭代更新，技术更新才能完成，比特币在设计上和公平性上都是没问题的，但是其实我们忽略了一个重要的问题-延迟性!我们发现想要完成一个技术迭代现在看来几乎是不可完成的，因为没有人愿意改变，可能这才是我们遇到的最大的问题吧!
Eit的房产网络区块链将会轻松的解决以上问题!
解决方案一：时效消费场景交易
消费场景在Eit的设计中主要分为两个层次-线上和线下，我们首先改变我们对钱包的认知，生命体的钱包首先是一个网络版本没有冷钱包的设计，主要就是为了解决交易的时效性。
线上交易：每一个需要支付环节的线上应用都可以对接我们的钱包API，快速完成交易，货币交割时间1-3秒。
线下交易：线下支付我们将提供一个类似的API给到支付工具的设计厂商，通过快速开发包，完成线下支付工具的开发，交易时间同样是1-3秒!
解决方案二：钱包绑定机制
首先我们在考虑一个问题-到底用户的凭证是什么?移动互联网时代，手机就是用户最时效和准确安全的凭证，我们的钱包设计基于对用户手机的绑定，通过绑定手机环节不仅可以有效解决账户遗失问题，继承问题同时有效解决!
解决方案三：去中心化的技术
这里为什么叫技术运营呢!其实技术的更新就是对整个体系的运营，我们在Eit设计了一个投票机制所有的钱包根据一个权重体系完成投票环节，通过权重体系的认定快速强制性完成钱包和矿机算力的更新!
未来已来，希望Eit的引入能够真正的革新整个区块链行业!
Cloud - referred to as "ETB, Chinese bits of Cloud, to solve the problems now block chain technology, by the world's largest currency in mid-may 2017 miners union launched ETBproject team, lasted six months, ETBby top encryption technology on the basis of succeeding to the good features of the currency of existing problems in innovation, ETBencryption currency a circulation of 21 million pieces, ETBblock using linear algorithm for mining action now, but using bionic property network force inheritance pattern, forming a network of virtual currency property, us to identify each account as a ETB, apply every payment settlement to complete the final payment of housing endings simulation done immediately.
Technology is making great originally complex world becomes simple. No more long, only for decades, the high and new technology such as computer, Internet, smart phones, let ordinary people once unimaginable transactions, such as global communication become reality and simple. At present in the field of more complex global real estate investment and financing, is also usher in a change to the simple. Thanks to block the rise of chain technology and intelligent use of contract, and by the Eit platform into reality.
ETBhope, through technology and intelligent use of investment contract based on block chain platform, link to global investors and real estate projects, and online visual rendering the whole real estate projects, from raw materials, logistics, to the completion of construction, to operation and benefits, etc., let the real estate investment in a transparent and easy to understand, predictable, through the platform of ETB, any investors can invest in real estate projects of any country, developers will also can more directly in the face of investors.
May recall our daily online life: when we phase of a proct, all fees paid to first trading platform, such as taobao or jingdong, and then wait for the businessman shipment, after we confirm receive the goods, the platform to transfer the cost to merchants. In the shopping process, we can believe that the strange sellers, because we have no choice but can only believe that the trading platform, otherwise, cannot trade. And based on block chain technology is not so complicated, in Eit platform, for example, investors and developers only need to believe that your judgment can direct interaction, Eit need to do, just for investors to strict audit status and real estate projects, normal trading platform and provide tokens, guaranteed.
If yesterday, block chain technology application is limited to a few financial sectors such as banking, securities, fund, so now, block chain have begun to directly affect the daily life of ordinary people, the emergence of Eit dispersible in real estate investment platform, as well as the block chain into the construction instry, changed our ideas about traditional in the field of real estate investment and financing, trust and cooperation have been so easy.
As COINS COINS community technology research and development center, at the same time shoulder the mission of the guide the whole instry technology innovation, we are in the process of evolving block chain technology, found that some fatal problems the instry! Including the currency block chain technology! So we started since 2018 to now block chain technology innovation and iteration, the following will be detailed in this paper, the problems and ETB block by block chain chain how to deal with these problems, at the same time announced life block chain core algorithm.
Problem a: block chain can't really into consumption scene!
The currency's long-term vision is digitally docking to the existing monetary system, for the currency to become real currency digital kernel, but whether the currency or other block chain technology can really achieve this goal, at least so far all chain blocks only have an attribute that is investment property, the problem is the main reason of the technology on a few questions, first of all, digital currency trading time, the existing block chain trading technology is unable to realize real-time transaction, because at the beginning of the design for the sake of safety and decentralization, we abandoned the timeliness of the method. Unable to complete real-time delivery, money is the biggest problem!
Problem two: block is lost!
This problem is a comprehensive problem, missing some blocks generally appear in several cases:
1, accounts tag missing
2, mill tag missing
3, all without effective inheritance
This problem seems to be very small, but for the influence of block chain is deadly, because after constantly lost finally the amount of blocks will be less and less, so the corresponding value will continue to increase, increase investment speculators driving force, to the health of a block chain development create a vicious cycle for a long time, and let the user to the whole block chain cannot be trusted.
Question 3: decentralized technology operations
COINS community is to the existence of decentralized technology updates, but we really can't finish the really good technology updated quickly because most of the cold wallet and ore confidential to accept this time iterative update, update technology to complete, the currency on the design and fairness are no problem, but actually we ignored an important part of the problem - the delayed! We found that want to complete a technical iteration now is almost impossible, because no one is willing to change, perhaps this is the biggest problem we met!
ETB property chain network blocks will be easy to solve the above problem!
Solution a: aging consumption trading scene
Consumption scenarios in the design of ETB - online and offline mainly divided into two levels, the first thing we change our cognition to the wallet, purse is first and foremost a network version of the life not cold purse design, main is to solve the timing of the deal.
Online transactions: each link need to be paid for the online application can be docking API, our wallet quickly complete the transaction, currency delivery time 1 to 3 seconds.
Offline payment: offline payment, we will provide a similar API to pay the tool design manufacturers, through rapid development kit, complete offline payment tool development, trading time is also 1-3 seconds!
Solution 2: wallet binding mechanism
First of all we are thinking about a question - what is the end user's credentials? Mobile Internet era, the mobile phone is the most limitation and accurate user security credentials, our wallet design based on the binding of user's phone, through binding mobile phone link not only can effectively solve the problem of account lost, succession and effectively solve!
Solution 3: decentralized technology
Why call technology operations here! Technical update is actually on the system's operation, we have design a voting mechanism in Eit all wallet, according to a weight system to complete the voting link through the weighting system of fast is mandatory to complete the wallet and mining machine force update!
Future has come, in the hope that the introction of the Eit can truly the innovation of the whole block chain instry!
Ⅳ 互联网上的虚拟货币
【互联网上的虚拟货币】
1、比特币
自2009年发布以来，比特币已成为最知名的虚拟货币。这一虚拟货币由化名为“中本聪”的个人或组织开发(其真实身份一直未知)，主要被在线商户使用。不过近年来，一些小型实体商户也开始接受比特币支付。通过复杂的算法和大量计算资源，用户可通过“挖矿”的方式来获得比特币，当然也可通过交易所或类似BitInstagnt和Coinbase的服务来购买比特币。可开采的比特币总量约为2100万个，而目前的开采量已超过1100万个。比特币已引起了Western Union、MoneyGram和PayPal等公司的关注。有消息称这些服务正在评估是否允许用户在各自平台上使用比特币。
2、Litecoin
Litecoin基于比特币协议，但支持更快的交易确认。这一系统内可开采的Litecoin总数为8400万个，到目前为止的开采量约为20%。根据该虚拟货币发明人查尔斯·李(Charles Lee)的说法，目前流通的Litecoin总价值约为5000万美元。他表示，并不清楚有任何实体商户接受Litecoin支付，但一些主机服务提供商已接受该虚拟货币。
3、Freicoin
与Litecoin类似，Freicoin同样基于比特币协议，但目前仍处于发展早期。根据该虚拟货币发明人之一马克·弗利邓巴赫(Mark Friedenbach)的说法，系统内可开采的Freicoin总数约为1亿个，目前开采量约为20%。Freicoin网络中当前的并发用户数约为100。目前只有很少的小型在线商户接受Freicoin，而该虚拟货币的发明人正在尝试更大范围的推广。
3、Ripple
Ripple既是一个支付网络，也是一种虚拟货币。Ripple协议的开发者是硅谷公司OpenCoin。该公司表示，其目标是让尽可能多用户使用Ripple。目前已开采的Ripple总数约为1000亿个，其中大部分都在OpenCoin手中。该公司联合创始人及CEO克里斯·拉尔森(Chris Larsen)表示，OpenCoin即将向约4万名用户发放每用户2000个Ripple，并计划在未来几年内共发放约500亿个Ripple。目前，消费者可通过Ripple.com网站注册以获得Ripple钱包，并利用第三方服务Bitstamp从银行帐户汇款，以使用Ripple钱包。
4、亚马逊Coins
亚马逊是少数几家自主开发虚拟货币的大型科技公司。大部分情况下，这些公司的虚拟货币只能在各自网站上使用。亚马逊于5月份刚刚推出亚马逊Coins服务，目前可用于在Kindle Fire平台，以及应用商店和网站上购买游戏、应用和其他数字内容。1美元可购买100个亚马逊Coins，而大量购买将获得折扣，例如1000个亚马逊Coins售价为9.5美元。
5、国内知名虚拟货币币
国内知名的虚拟货币如网络公司的网络币、腾讯公司的Q币，Q点、盛大公司的点卷，新浪推出的U币米票(用于iGame游戏)，侠义元宝(用于侠义道游戏)，纹银(用于碧雪情天游戏)等等还有很多游戏币。