Monday, October 3, 2022

How To Retrieve Data From Blockchain

Try The Ethereum Sql Search Engine Yourself

How to store Data in Ethereum Blockchain? (No previous programming skills required)

To access the raw SQL interface you first need to retrieve your access credentials. You can register for a free account and get the SQL access credentials right now at in just a few seconds .Then you need to to access our Ethereum database. We suggest the free PGAdmin4, but any other client supporting PostgreSQL 11 will do.

Setup your SQL connection as mentioned in the account backend. If you need help or any errors occur, please dont hesitate to ask us for assistance.You can find our SQL documentation here, including a database schema description with the entity-relationship diagram as well as a brief SQL tutorial.

However, please keep in mind that the Ethereum SQL interface is still in beta, hence the service might not be constantly available and the database schema could change from one day to another.

We might also be able to help you to pin down and visualize the data relevant to your specific use case. Just email us at we are excited to see our data used in many new ways!

Why Are They Needed

With a blockchain like Ethereum, you need every node in the network to replay every transaction and end up with the same result, guaranteed. APIs introduce potentially variable data. If you were sending ETH based on an agreed $USD value using a price API, the query would return a different result from one day to the next. Not to mention, the API could be hacked or deprecated. If this happens, the nodes in the network wouldn’t be able to agree on Ethereum’s current state, effectively breaking consensus.

Oracles solve this problem by posting the data on the blockchain. So any node replaying the transaction will use the same immutable data that’s posted for all to see. To do this, an oracle is typically made up of a smart contract and some off-chain components that can query APIs, then periodically send transactions to update the smart contract’s data.

How Sap Hana Blockchain Works

My last blog already gave an impression on how SAP HANA blockchain works and which components are involved in getting blockchain data into a SAP HANA database. With this blog, Id like to provide some more details on these components and their interplay, as well as the features that they enable.

An important fact and common source of misunderstandings is that SAP HANA is not acting as a node in a blockchain network all by itself. It is instead leveraging the SCP Blockchain Service as a gateway. The interaction with the network is managed by the SCP blockchain service. The blockchain network itself consists of different nodes that can be hosted on SAP Cloud Platform, any other cloud service provider or even on-premise. Additional services like the HANA integration and other application enablement services are only available if the blockchain node is hosted on SCP.

The SAP HANA Integration Service connects the SCP Blockchain service to SAP HANA. It is also used to configure the connection properties on SCP side. This includes the mapping of blockchain messages to the columns of a database table, read/write or read-only access and table types. There are three types of tables.

Ledger and worldstate tables contain transaction-specific information as well, like the timestamp and block number.

Also Check: How Do I Find My Lost Bitcoins

What Is The Content Of A Blockchain

A blockchain is an immutable, append-only distributed database. To work with a blockchain, it is not just about understanding these unique features, but one also needs to understand what data is saved on the blockchain. What does blockchain data look like, i.e. what is the content and how is it formatted?

As the word describes, a blockchain is a chain of blocks, and it works similarly for the existing major chains like Bitcoin, Ethereum, and other Proof-of-Work networks. To simplify, in this article the focus is on the Ethereum blockchain only. Technical details that are not actual data but mainly support the functioning of the network are intentionally left out.

Each block consists of the header and the transactions mined with the block. The chain is formed by hashing various information of the previous block and including it in the new block header.

Besides this hash of the previous header, in Ethereum there are hashes of the state root and the roots of the transactions and the receipt see here for details.

Of course, there is also a block number , a timestamp, and information about the gas limit and gas usage. In addition, there are some pieces related to the mining process .

Check out this post for some diagrams and more details.

Benefits Of Smart Contracts

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Speed, efficiency and accuracy

Once a condition is met, the contract is executed immediately. Because smart contracts are digital and automated, theres no paperwork to process and no time spent reconciling errors that often result from manually filling in documents.

Trust and transparency

Because theres no third party involved, and because encrypted records of transactions are shared across participants, theres no need to question whether information has been altered for personal benefit.


Blockchain transaction records are encrypted, which makes them very hard to hack. Moreover, because each record is connected to the previous and subsequent records on a distributed ledger, hackers would have to alter the entire chain to change a single record.


Smart contracts remove the need for intermediaries to handle transactions and, by extension, their associated time delays and fees.

Read Also: How To Buy And Sell Bitcoin And Make Profit

Storing A Subset Of The Data On The Blockchain

We can get back those benefits to a certain degree, by storing the hash of the data and parts of the data on the blockchain.

Depending on the parts of the data we get back some transparency, because the data is now publicly accessible again.

Also, the subset of the data is stored decentralized instead of stored in a central database.

Dont Trust Verify: Transactions Are There For All To See

Cryptocurrencies like Bitcoin are very unique when comparing them to traditional money. They make use of a technology called blockchain. This is, in short, a distributed ledger of all transactions. What this means is that all the transactions ever made for each cryptocurrency are recorded on a single blockchain, holding its entire history.

Remember how you would keep your receipts and check your bank account each month, just to make sure that all transactions on it were correct? Or perhaps you just trusted your bank instead. Well, with cryptocurrencies, you dont need to trust anyone there are no third parties involved. Nearly all cryptocurrencies use public blockchains, where every detail of each transaction ever made can be seen.

What does this mean for you? Well aside from being able to see how much richer others might be than you, it actually serves a very valuable purpose: you can verify each transaction youve ever sent or received. If you feel like the service you are using isnt showing the correct amount of Bitcoins, you can take a look for yourself and see whether it matches. Also if your friend promised he made the transaction already even though you havent received it, you can check the validity of their claim directly on the blockchain itself. As the famous saying goes: Dont trust, verify with cryptocurrencies, you can verify everything relating to transactions. So how can you check the entire history of a blockchain?

Recommended Reading: How To Buy Bitcoin On Blockchain

Recover A Wallet From A Computer That Turns On But Wont Boot

If you use Bitcoin Core and your computer wont boot or start up properly, use a Linux Live DVD or Live USB to start the computer and access your hard drive. You should then search for the file named wallet.dat, which is in your Windows AppData directory, or under the .bitcoin directory in Linux. Copy that file to an external drive and then transfer it to the same directory on a new computer with Bitcoin Core installed. Run Bitcoin Core afterwards and allow it to rescan and sync.

To recover a Wasabi Bitcoin wallet from a computer with a functioning drive but which isnt booting, you need to find the wallet*.json file on your computer and copy it to an external drive which you can use to copy it to a new computer under the same directory with Wasabi installed on it. This file is located in the clients > > Wallets directory. On Linux, that is found in the .walletwasabi folder. This is a hidden directory and you may need to press Ctrl + H to reveal it.

Ledger Live And Block Explorers

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Whenever you start up Ledger Live, it synchronizes with blockchains to check for any new transactions or changes to your balance as well as how much your cryptocurrencies are currently worth. It updates this frequently when in use as well, to make sure it remains up to date.

However, its also important that you can check all the details of your past or incoming transactions. When you click on any transaction shown in Ledger Live, it will already show you the details. We do, however, also give you the opportunity to check a block explorer here so you can verify it there as well. This can be done by clicking on View in Explorer. You can from there also continue to check your addresss balance and verify that Ledger Live is showing the correct amount. In case of any outage in Ledger Live, a block explorer will always be able to show you how much of a certain cryptocurrency you currently have.

With Ledger Live, we empower you to easily look up your balances even when not using your hardware wallet. And it can do so much more learn more about its powerful features here.

Keep learning! If you enjoy getting to grips with crypto and blockchain, check out our School of Block video Blockchain Real Use Cases.

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How To Use The Graph

Running your own Graph instance can help to be fully independent from the service and is totally fine as long as the code is open-sourced. On the other hand, it might cause certain inconveniences, as you will have to count additional hours for upgrading every time the new features come in.

The second option is to use the hosted service provided by The Graph. The service combines its own network of Curators, Delegators and Indexers who operate within the system to ensure indexing and query processing. Its worth noting that using the hosted solution will be accompanied by the query fees for service providers.

Why We Added Sql Access Besides Elasticsearch

Our Elasticsearch index of the Ethereum blockchain offers lightning-fast access to the data, even for complex queries down to the smart contract event level. So why add an SQL database ?

The main reason is that a lot more people are familiar with SQL as a query language than with the Elasticsearch Query DSL. SQL has been around a lot longer and the SQL standard has been followed very closely by many different commercial and open-source SQL database products. Also, quite a number of people that are not developers themselves can use or at least read SQL queries. And while many business domain users will require charts and diagrams when discussing data, most of them are familiar with the table format of rows and columns and might even know how to combine and aggregate things from using Excel spreadsheets.The visualization layer is another reason why we offer the Ethereum data via SQL. While Elasticsearch can be included in many business intelligence tools like Grafana, Kibana, or Plotly, there is a whole other set of programs or libraries available like Tableau, QlikView, or Jetbrains DataGrip that will interface more easily with SQL data.

Also Check: Is Bitcoin Cash Better Than Bitcoin

How To Speed Up Reading Blockchain Data

To monitor smart contract development either on a test net or Ethereum Mainnet one needs to set up a node and create some sort of index in other words a database.

Doing so there are essentially two options: a) index the whole blockchain or b) limit the amount of data that is drained from the node into the index. Which approach to choose is a question of balance between resource consumption and flexibility constraints. In any way, the necessity for a filter mechanism for the relevant data arises.Depending on the amount and type of data that you want to access, another thoughtful consideration should be made about how to query your blockchain index. The query language and the database system are, of course, mostly interdependent, so youll need to consider both in tandem.

Popular choices tend to be SQL or Elasticsearch Query DSL as many developers are familiar with their query syntax.

These architectural considerations become more complex if you want to share such a database index across your teams/departments or even between several business entities. This would at least require authentication, likely also authorization, and possibly even accounting.

Lets assume you have made up your mind about these considerations, have acquired the infrastructure, and set up the systems. Now youll do classical extract, transform and load processes.

How To Use Chainlink Oracles

What is the relation between Blockchain and Crypto

Note: Were using the Ropsten testnet in this example.

Letsassume that we want to create a smart contract that acts upon the USD price of Ethereum, as reported from the popular price analysis site CoinGecko. We know that there is no native way our smart contract can call an external HTTP API, but an oracle node can.

Using the request-and-response cycle, our smart contract can request data from an oracle node, configured to perform HTTP GET requests, and implement a callback function for the oracle to fulfil with a response.

We cant use any oracle, because each is configured to perform specific tasks depending on their support. To find a high-quality oracle to suit our needs, we must search for one using a listing service like Chainlink Market.

Recommended Reading: How Do Crypto Taxes Work

Synchronizing Sap Hana And Scp Blockchain Service

SAP HANA uses Smart Data Integration to retrieve data from and send data to the SCP Blockchain service. Three components are involved in this.

  • The data provisioning server is part of SAP HANA.
  • Data provisioning adapters are specific to each type of data source. SDI is delivered with a set of predefined adapters for various remote sources, but also provides an SDK for custom built adapters.
  • Data provisioning agents host data provisioning adapters. Agents can be deployed on any server that has a network connection to SAP HANA and the remote source in this case your Blockchain in SCP. Deploying it on the same server as SAP HANA is possible as well, although it is recommended to deploy it as close to the data source as possible.

Where Did My Data Go Querying Data From The Blockchain

Alright. Despite the problems described above, we somehow managed to get our data on the blockchain…

How do we get the back, in case we need them?

A blockchain is no SQL server where we could query for our data.

In fact, most blockchains only allow for downloading transactions by their id .

So how do we solve all these problems?

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How To Store Data On Ethereum Blockchain

Since 2009, we have heard a lot about Blockchain, its application, and growth. There are some positives and negatives to this technology. But, one common thing is that this technology is growing at a faster pace. When we talk about Blockchain, then there is another parameter that we should not, and thats data storage. We all know that Blockchain is a ledger which allows the exchange of information and this information is stored in the ledger. Well, our focus in this blog would be on Ethereum. It is not just a cryptocurrency, and there is much more to it. Till now we had discussed use cases of Blockchain, but here we will talk about data storage on Ethereum Blockchain.

How To Read A Blockchain Transaction History

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Key Takeaways:
Blockchains are public ledgers, meaning anyone can see all transactions ever made You can use Block Explorers to easily navigate and search your blockchain transaction history A transactions main elements are: the Transaction ID, the sending & receiving address, the associated fees and the transactions status Ledger Live allows you to easily access blockchain explorers for each transaction

Cryptocurrencies are known to be completely transparent and that all transactions are verifiable. However, not everyone might know exactly how this works. Today, wed like to show how you can start verifying your blockchain transaction history and balances for yourself through a block explorer.

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Transform Data Into A Human

In the transformation step, you probably want to make the data human-readable. Examples might be labeling Ethereum accounts of known origin , or fetching smart contract Application Binary Interfaces to spell out the names of the functions. Youll use some form of mapping to match the raw data to the clear text labels. This could also mean getting historical price information for ERC-20 tokens for example and combining the timestamp with the appropriate block height. Youd need that to quantify value transfer transactions in fiat denominations, which would be an example of enriching the blockchain data from external sources.

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