SQL : PostgreSQL

  Aggregate Functions Like most other relational database products,  PostgreSQL  supports  aggregate functions . An aggregate function computes a single result from multiple input rows. For example, there are aggregates to compute the  count ,  sum ,  avg  (average),  max  (maximum) and  min  (minimum) over a set of rows. As an example, we can find the highest low-temperature reading anywhere with: SELECT max(temp_lo) FROM weather; max ----- 46 (1 row) If we wanted to know what city (or cities) that reading occurred in, we might try: SELECT city FROM weather WHERE temp_lo = max(temp_lo); WRONG but this will not work since the aggregate  max  cannot be used in the  WHERE  clause. (This restriction exists because the  WHERE  clause determines which rows will be included in the aggregate calculation; so obviously it has to be evaluated before aggregate functions are computed.) However, as is o...
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**** RESOURCES to learn more languages

 


Ways to learn about programming

Writing programming language code can be an exciting and rewarding experience. The programming field has a long history of people helping each other improve their skills and develop best practices. You will focus on the R programming language in this course, but in the future you might choose to pursue additional programming languages based on your interests and professional goals. This reading is a general guide to help you decide which programming languages are best suited for you.

Image of a person sitting at a desk and typing on a keyboard. There are 4 large computer screens in front of them.

Popular programming languages by profession 

Let’s go through some potential job titles you might encounter and the most popular programming languages used in those professions. Also included is a list of additional resources for you to explore and learn more about each of the programming languages introduced.

Data analyst

A data analyst collects, transforms, and organizes data to draw conclusions, make predictions, and drive informed decision-making. The most popular programming languages used by data analysts are R and Python. 

R offers convenient statistical features for data analysis and is useful for creating advanced data visualizations. Check out these resources to learn more about R:

Python is a general-purpose language that you can use to create what you need for data analysis. Here are a few resources to begin learning Python:

Web designer

A web designer is responsible for the styling and layout of web pages containing text, graphics, and video. Web designers generally use Hypertext Markup Language v5 (HTML5) and Cascading Style Sheets (CSS) to create web pages. 

HTML5 provides structure for web pages and is used to connect to hosting platforms. Learn more about HTML5 and CSS using these resources:

CSS is used for web page design and controls graphic elements (color, layout, and font) and page presentation on multiple devices (large screens, mobile screens, and printers). Check out these cheat sheets for CSS:

Mobile application developer

A mobile application developer uses programming to create applications used on laptops, mobile phones, and tablets. The most popular programming languages for mobile application developers are Swift, Java, and C#.

Swift (for Apple platforms) is an open source scripting language for macOS, iOS, watchOS, and tvOS. Its main goal is to make applications run faster. Browse these resources for more information about Swift:

  • Swift.org: an open source community with resources to learn how to use Swift, including videos and sample code

  • Swift developer site: an Apple developer website with information for developers who want to use Swift 

  • Swift development resources: Apple’s collection of documentation, sample code, videos, and recommended books 

Java (for Android devices) is the official language for Android development. The article I want to develop Android apps - which languages should I learn? explores some other languages used for Android development. Check out these resources for Java:

C# (pronounced C-sharp) is an object-oriented programming language that is widely used to create mobile apps in the .NET open source developer platform. Xamarin extends the .NET platform with a framework for developers to create cross-platform mobile apps for both iOS and Android. Here are a few resources to help you learn C#:

Web application developer

A web application developer designs and develops network applications used across the web. The most popular programming languages used by web application developers are Java, Python, Ruby, and PHP.

Java is widely used to create enterprise web applications that can run on multiple clients. Java’s main strength is its “Write Once, Run Anywhere” (WORA) approach.Browse these resources to learn more about Java:

Python is a general-purpose programming language. Check out the Python resources listed in the data analyst section.

Ruby is a general-purpose, object-oriented programming language used for web application development. Ruby isn't the same as Ruby on Rails, which is an open source web application framework that runs using Ruby. Browse these resources to learn more about Ruby: 

  • Ruby news: information about the latest Ruby releases and links to other resources

  • Ruby documentation: includes guides, tutorials, and reference material to help you learn more about Ruby

  • Ruby programmer’s guide: a tutorial and reference guide for Ruby

  • Learn Ruby from Codecademy: a website with free basic interactive lessons, and additional activities that can be accessed with a monthly subscription

PHP is a scripting language particularly suited for web application development. It was based on Perl, another programming language. PHP is simple, flexible, and relatively easy to learn. Check out these resources to learn more about PHP:

Game developer

A game developer is an application developer who specializes in video game creation. Game developers most commonly use the programming languages C# and C++.

C# is an object-oriented programming language that is widely used to create games. Check out the C# resources listed in the mobile application developer section.

C++ is an extension of the C programming language that is also used to create console games, like those for Xbox. Browse more information about C++:

Tips for learning programming languages

Here are a few tips to follow when you start learning a new programming language:

  • Define a practice project and use the language to help you complete it. This makes the learning process more practical and engaging.  

  • Keep previous concepts and coding principles in mind. Many of these are transferable between programming languages. So, after you have learned one language, learning a second or third programming language tends to be much easier. 

  • Create and keep good notes and cheat sheets in whatever format (handwritten or typed) that works best for you.

  • Create an online filing system for information that you can easily access while you work in various programming environments.


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