Tutorial by Examples: u

Subqueries in FROM clause

You can use subqueries to define a temporary table and use it in the FROM clause of an "outer" query. SELECT * FROM (SELECT city, temp_hi - temp_lo AS temp_var FROM weather) AS w WHERE temp_var > 20; The above finds cities from the weather table whose daily temperature variation i...

SQL • Subqueries

Subqueries in WHERE clause

The following example finds cities (from the cities example) whose population is below the average temperature (obtained via a sub-qquery): SELECT name, pop2000 FROM cities WHERE pop2000 < (SELECT avg(pop2000) FROM cities); Here: the subquery (SELECT avg(pop2000) FROM cities) is used to s...

SQL • Subqueries

Subqueries in SELECT clause

Subqueries can also be used in the SELECT part of the outer query. The following query shows all weather table columns with the corresponding states from the cities table. SELECT w.*, (SELECT c.state FROM cities AS c WHERE c.name = w.city ) AS state FROM weather AS w;

SQL • Subqueries

Tuples

b = {:ok, 1, 2} Tuples are the equivalent of arrays in other languages. They are stored contiguously in memory.

Elixir Language • Data Structures

Complex Data (Protobuf)

StackExchange.Redis also supports sending bytes over the pub/sub channel, here we use protobuf-net to serialize our message to a byte array before sending it: // definition of a message (marked up with Protobuf attributes) [ProtoContract] public class ChatMessage { [ProtoMember(1)] pub...

StackExchange.Redis • Publish Subscribe

Subscript/Superscript

x<sub>2</sub> produces x2 x<sup>2</sup> produces x2

Markdown • Text Formatting

Compare NSURL

NSString *urlString = @"https://www.stackoverflow.com"; NSURL *myUrl = [NSURL URLWithString: urlString]; NSURL *myUrl2 = [NSURL URLWithString: urlString]; if ([myUrl isEqual:myUrl2]) return YES;

Objective-C Language • NSURL

Using IBInspectable and IBDesignable

One (or two) of the coolest new features in recent Xcode releases are the IBInspectable properties and IBDesignable UIViews. These have nothing to do with the functionality of your application but instead impact the developer experience in Xcode. The goal is to be able to visually inspect custom v...

iOS • UIView

Installation or Setup

Detailed instructions on getting mapbox set up or installed.

mapbox • Getting started with mapbox

Use the `email` as username and get rid of the `username` field

If you want to get rid of the username field and use email as unique user identifier, you will have to create a custom User model extending AbstractBaseUser instead of AbstractUser. Indeed, username and email are defined in AbstractUser and you can't override them. This means you will also have to r...

Django • Extending or Substituting User Model

Basic Setup

Backbone requires Underscore and (optionally) jQuery - for DOM manipulation (using Backbone.View) and RESTful persistence. The quickest way to get up and running with Backbone is to create an index.html file with simple script tags in the HTML <head>: <html> <head> ...

backbone.js • Getting started with backbone.js

Example usage

Read text file from path: val sc: org.apache.spark.SparkContext = ??? sc.textFile(path="/path/to/input/file") Read files using wildcards: sc.textFile(path="/path/to/*/*") Read files specifying minimum number of partitions: sc.textFile(path="/path/to/input/file&qu...

apache-spark • Text files and operations in Scala

Recursive functions

A recursive function is a function that calls itself in its definition. For example the mathematical function, factorial, defined by factorial(n) = n*(n-1)*(n-2)*...*3*2*1. can be programmed as def factorial(n): #n here should be an integer if n == 0: return 1 else: ...

Python Language • Functions

Sending a minimal HTTP request manually using Telnet

This example demonstrates that HTTP is a text-based Internet communications protocol, and shows a basic HTTP request and the corresponding HTTP response. You can use Telnet to manually send a minimal HTTP request from the command line, as follows. Start a Telnet session to the web server www.e...

HTTP • HTTP requests

HTTP Analytics through an Event Emitter

In the HTTP server code (e.g. server.js): const EventEmitter = require('events') const serverEvents = new EventEmitter() // Set up an HTTP server const http = require('http') const httpServer = http.createServer((request, response) => { // Handler the request... // Then emit an event...

Node.js • Event Emitters

What is Selenium WebDriver ?

Selenium is a set of tools designed to automate browsers. It is commonly used for web application tests across multiple platforms. There are a few tools available under the Selenium umbrella, such as Selenium WebDriver(ex-Selenium RC), Selenium IDE and Selenium Grid. WebDriver is a remote control i...

selenium-webdriver • Getting started with selenium-webdriver

Create a string with strikethrough text

Objective-C NSMutableAttributedString *attributeString = [[NSMutableAttributedString alloc] initWithString:@"Your String here"]; [attributeString addAttribute:NSStrikethroughStyleAttributeName value:@2 range:NSMakeRange(0, [attributeString length...

iOS • NSAttributedString

Installation or Setup

AEM can be installed as a standalone executable JAR file or through web application servers, such as JBoss and WebSphere, as a WAR file. Prerequisites AEM 6.2 needs at minimum the following in order to run Java Runtime Environment (JRE) 1.8x (64bit) 5GB of free disk space for installation 2GB...

aem • Getting started with aem

Multiple Line

/* This is a CSS comment */ div { color: red; }

CSS • Comments

Working with null-string when parsing json

{ "some_string": null, "ather_string": "something" } If we will use this way: JSONObject json = new JSONObject(jsonStr); String someString = json.optString("some_string"); We will have output: someString = "null"; So we need to...

Android • JSON in Android with org.json