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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

Storage area network: Quick Definition

SANs are primarily used to enhance storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear to the operating system as locally attached devices. A SAN typically has its own network of storage devices that are generally not accessible through the local area network (LAN) by other devices. The cost and complexity of SANs dropped in the early 2000s to levels allowing wider adoption across both enterprise and small to medium-sized business environments.   Best Uses of Storage Area Networks A SAN does not provide file abstraction, only block-level operations. However, file systems built on top of SANs do provide file-level access, and are known as shared-disk file systems. More to read: Best SAN Storage area networks acronyms Top 20 benefits of SAN Storage area networks

SAN: Real Architecture Explained

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A SAN is connected behind the servers. SANs provide block-level access to shared data storage. Block level access refers to the specific blocks of data on a storage device as opposed to file level access. One file will contain several blocks. Storage Area Networks (SANs) SANs provide high availability and robust business continuity for critical data environments. SANs are typically switched fabric architectures using Fibre Channel (FC) for connectivity. The term switched fabric refers to each storage unit being connected to each server via multiple SAN switches also called SAN directors which provide redundancy within the paths to the storage units. This provides additional paths for communications and eliminates one central switch as a single point of failure. Ethernet has many advantages similar to Fibre Channel for supporting SANs. Some of these include high speed, support of a switched fabric topology, widespread interoperability, and a large set of management tools. In a st

Storage area network (SAN): Networks Vs Configurations

These are most popular terms used in Storage area networks area. Every developer must know these terms clearly. Highly useful to explain in interviews. Frequently used terminology in SAN given below for your quick reference. 

SAN Vs NAS Benefits, Differences

SANs are particularly helpful in backup and disaster recovery.  Within a SAN, data can be transferred from one storage device to another without interacting with a server. 

SAN Storage: All about its 4 Real Usages

The storage area network fundamentals everyone must know you understand about applications. These applications may refer to horizontal applications (e.g., backup, archiving, data replication, disaster protection, and data warehousing) or vertical applications (e.g., online transaction processing (OLTP), enterprise resource planning (ERP) business applications, electronic commerce, broadcasting, prepress, medical, and geophysics). SAN is also well suited to making performance and high availability more scalable and more affordable in applications such as clustering and data sharing. This article discusses two major horizontal applications, backup and data sharing, and how they interact with SAN. The other important point is, if you are a job seeker the below list is helpful. This is just a like a one time SAN interviews refresher. So you can do well in interviews. 1. Realtime (or window-less) backup The importance of window-less backup (also called hot backup) becomes obvious when it a

20 Top Benefits of SAN (storage area network)

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In my previous post I have covered about fundamentals of SAN (storage area networks). The below are the list of top 20 benefits of storage area networks.   What are the major benefits of san Greater performance: Current Fibre Channel SANs allow connection to disks at hundreds of megabytes per second; the near future will see speeds in multiple gigabytes to terabytes per second. Increased disk utilization: SANs enable more than one server to access the same physical disk, which lets you allocate the free space on those disks more effectively. Higher availability to storage by use of multiple access paths: A SAN allows for multiple physical connections to disks from a single or multiple servers. Deferred disk procurement: That’s business-speak for not having to buy disks as often as you used to before getting a SAN. Because you can use disk space more effectively, no space goes to waste. Reduced data center rack/floor space: Because you don’t need to buy big servers with room for lot

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. 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