According to LearnCodeAcademy’s video on Node JS, the following is a brief intro to Node.js. The creators of Node, took JavaScript, which is normally confined to a web browser, and they allowed it to run on your computer. A JavaScript engine for google chrome can now run on your machine. JavaScript in this new environment allows us to do things like; listen for network traffic, access files on our computer, listen to HTTP requests your computer receives and send back a file.
Today we will be talking about SQL joins, a powerful way to relate and aggregate data across many tables. First, lets start with definitions of each.
A SQL join clause is a way to combine ROWS from two or more tables, based on a common column between them. After a join CLAUSE, or join QUERY is preformed, we have essentially search RESULTS. The data may be coming from multiple tables, and we may rename columns, but the final product is simply a search result. There is no manipulation of tables in the database, only extractions.
Let’s start with some basic definitions of keywords.
##Authentication is how a website determines the content a user sees and the features they are allowed to use. It’s like when you arrive at the restaurant and they say, ‘Who are you? (username and password), and then they lead you to your table (features/content that you are have permission to use/see). Or more simply, ‘who gets to see and do what’ on a web application. The specifics around this type of control system is based on four main pillars, which I will summarize below.
Let’s start with the basics. Generally speaking, JavaScript is single threaded, meaning everything else in the subsequent code is blocked until the current task is completed. Essentially, each operation occurs in order, one after another. We call this work flow synchronous. Most operations in javascript are performed synchronously. However, there are some disadvantages to synchronous code. Because each action is ‘blocking’, the DOM is paused/frozen or unavailable until the task is complete, leaving the user waiting on a locked browser to open up. If we need to load a bunch of data, the browser may lock up for an unreasonable amount of time while the data is loading. This is unpleasant for the user!