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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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SAN real configuration ideas to speed the devices

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In today’s terms, the technical description of a SAN (Storage Area Network) is a collection of computers and storage devices, connected over a high-speed optical network and dedicated to the task of storing and protecting data. In a nutshell, you use a SAN to store and protect data. 

A SAN uses the SCSI (Small Computer Storage Interconnect) and FC (Fibre Channel) protocols to move data over a network and store it directly to disk drives in block format.
SAN configuration ideas
Photo credit: Srini

SAN Configuration

Today, that high-speed network usually consists of fiber-optic cables and switches that use light waves to transmit data with a connection protocol known as Fibre Channel. (A protocol is a set of rules used by the computer devices to define a common communication language.) More and more, regular Internet protocol (IP)–based corporate networks, and even the Internet, are being used as the network part of a SAN. 

Nowadays Internet is the part of SAN

IP Networks

  • IP networks that are already in place can be used by other storage connection protocols such as iSCSI (internet Small Computer Storage Interconnect) to move and store data.
  • Using a network to create a shared pool of storage devices is what makes a SAN different. A SAN moves data among various storage devices, allows sharing data between different servers, and provides a fast connection medium for backing up, restoring, archiving, and retrieving data. 

SAN Devices

  • SAN devices are usually bunched closely in a single room, but they can also be connected over long distances, making a SAN very useful to large companies. Many of today’s SAN components are pretty much plug-and-play. To create a simple SAN, you just connect all the devices together with cables, and off you go. Creating larger SANs with many storage switches can become complex.

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