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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

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 Here are the five top commonly asked SQL queries in the interviews. These you can expect in Data Analyst, or, Data Engineer interviews. Top SQL Queries for Interviews 01. Joins The commonly asked question pertains to providing two tables, determining the number of rows that will return on various join types, and the resultant. Table1 -------- id ---- 1 1 2 3 Table2 -------- id ---- 1 3 1 NULL Output ------- Inner join --------------- 5 rows will return The result will be: =============== 1  1 1   1 1   1 1    1 3    3 02. Substring and Concat Here, we need to write an SQL query to make the upper case of the first letter and the small case of the remaining letter. Table1 ------ ename ===== raJu venKat kRIshna Solution: ========== SELECT CONCAT(UPPER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, 2))) AS capitalized_name FROM Table1; 03. Case statement SQL Query ========= SELECT Code1, Code2,      CASE         WHEN Code1 = 'A' AND Code2 = 'AA' THEN "A" | "A
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The Essential Guide to Blockchain Terminology

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Bitcoin was the first project developed by using blockchain. My post is to share Blockchain keywords by using an example of Bitcoin.

blockchain glossary


Let us ready...

Blockchain is new technology. Understanding its principles makes you helpful to apply in your projects. 

Initially, the purpose of Blockchain development was to carry mining. In general, mining means search and find value. Usually, mining processes are two types. Those are data mining and bitcoin mining.

Blockchain Glossary

  1. Blockchain - only blocks involved. The data which was finalized stored in blocks.
  2. Bitcoin Ledger - It is a public ledger
  3. Ledger or Blockchain - The chain of blocks
  4. Functions of Blockchain - It validates each transaction, Keeps track, and verifies ownership
  5. Double Spending- It prevents duplicating the Cryptocurrency for using next time.
  6. Consensus mechanism - It is also called PoW (proof of work). This mechanism avoids double-spending
  7. Group of Transactions - When a new group of transactions created, those will be added to the blockchain.
  8. Hash - Group of transactions created a Hash. This hash will be stored along with a group of transactions in the Blockchain. Hashing is the top security mechanism in the blockchain.
  9. Mining - It doesn't create Bitcoins and alter or modify blockchain. The miners will be rewarded with Bitcoins

Blockchain types


Here are three types of Blockchains

Private blockchains

  • Private blockchains are great for developers because they allow them to test ideas without using cryptocurrency. The developers’ ideas can remain a secret as well because the data has not been published publicly.
  • Large institutions can capitalize on the security and permanence of blockchain technology without their transactions being public the way they are in traditional blockchains.

    Public Blockchains

    • Public blockchains are available to the general public. An example is buying an art piece from a vendor located in another country.

    Hybrid Blockchains

    • These are a combination of public and private.

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