Tutor profile: Max A.
Subject: SQL Programming
What is SQL?
Many computer programs, including web-based programs like blogs, photo galleries and content management systems need to store and retrieve data. For example, blog software need to store the posts (ie, articles) you write, and retrieve them when a visitor goes to your site. Similarly, photo galleries store information about their pictures (for example, for sites that allow users to rate the photos, the numerical rating for each picture is stored in a database). Instead of reinventing the wheel and implementing their own system of storing and retrieving data, these software simply use the specialised database programs (example MySQL, Oracle, MS SQL, etc) To make it easy for other programs to access data through them, many database software support a computer language called "SQL" (often pronounced as "sequel"). SQL was specially designed for such a purpose. Programs that want the database software to handle the low-level work of managing data simply use that language to send it instructions. There are many databases that support the use of SQL to access their data, among them MySQL and PostgreSQL. In other words, MySQL is just the brand of one database software, one of many. The same goes for PostgreSQL. These two databases are very popular among programs that run on websites (probably because they are free), which is why you often see one or both of them being advertised in the feature lists of web hosts, as well as being listed as one of the "system requirements" for certain web software (like blogs and content management systems).
Whats a database?
A database is just a collection of data. Specialised database software (for example MySQL, Oracle, MSSQL etc), are just programs that lets you store and retrieve that data as efficiently as possible. A little analogy may help make it clearer why we use specialised database software. Think about the documents stored on your computer. If you were to save all your documents using a (brain-dead) file naming scheme like "1.doc", "2.doc", "3.doc", ... "9,999,999.doc" (etc), you will eventually face a problem of finding the right file if you're looking for a specific document. For example, if you're looking for a business proposal you made some time ago to XYZ Company, which file should you open? One way is to sequentially check every single file, starting from "1.doc", till you get the right data. But this is obviously a highly inefficient method of getting the right file. And it's primarily the result of an inefficient method of storing your data (ie, saving your files) in the first place.
Subject: Computer Networking
What does Virtual Local Area Network (VLAN) mean? and what are its key benefits.
Computer networks can be segmented into local area networks (LAN) and wide area networks (WAN). Network devices such as switches, hubs, bridges, workstations and servers connected to each other in the same network at a specific location are generally known as LANs. An LAN is also considered a broadcast domain. A VLAN allows several networks to work virtually as an LAN. One of the most beneficial elements of a VLAN is that it removes latency in the network, which saves network resources and increases network efficiency. In addition, VLANs are created to provide segmentation and assist in issues like security, network management and scalability. Traffic patterns can also easily be controlled by using VLANs. The key benefits of implementing VLANs include: -Allowing network administrators to apply additional security to network communication -Making expansion and relocation of a network or a network device easier -Providing flexibility because administrators are able to configure in a centralized environment while the devices might be located in different geographical locations -Decreasing the latency and traffic load on the network and the network devices, offering increased performance VLANs also have some disadvantages and limitations as listed below: -High risk of virus issues because one infected system may spread a virus through the whole logical network -Equipment limitations in very large networks because additional routers might be needed to control the workload -More effective at controlling latency than a WAN but less efficient than a LAN
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