Tutorial by Examples: er

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...

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;

NSArray *reversedArray = [myArray.reverseObjectEnumerator allObjects];

Property observers respond to changes to a property's value. var myProperty = 5 { willSet { print("Will set to \(newValue). It was previously \(myProperty)") } didSet { print("Did set to \(myProperty). It was previously \(oldValue)") } } m...

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

A Hash includes the Enumerable module, which provides several iteration methods, such as: Enumerable#each, Enumerable#each_pair, Enumerable#each_key, and Enumerable#each_value. .each and .each_pair iterate over each key-value pair: h = { "first_name" => "John", "last_na...

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...

C# has several operators that can be combined with an = sign to evaluate the result of the operator and then assign the result to the original variable. Example: x += y is the same as x = x + y Assignment operators: += -= *= /= %= &= |= ^= <<= >>=

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...

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...

The s interpolator allows the usage of variables within a string. val name = "Brian" println(s"Hello $name") prints "Hello Brian" to the console when ran.

Given the following CSV file: Id,Name 1,"Joel" 2,"Adam" 3,"Ryan" 4,"Matt" You can read the data with the following script: #r "FSharp.Data.dll" open FSharp.Data type PeopleDB = CsvProvider<"people.csv"> let people = Pe...

String concatenation can be performed using the + operator. For example: String s1 = "a"; String s2 = "b"; String s3 = "c"; String s = s1 + s2 + s3; // abc Normally a compiler implementation will perform the above concatenation using methods involving a StringBui...

List.map : (a -> b) -> List a -> List b is a higher-order function that applies a one-parameter function to each element of a list, returning a new list with the modified values. import String ourList : List String ourList = ["wubba", "lubba", "dub",...

List.filter : (a -> Bool) -> List a -> List a is a higher-order function which takes a one-parameter function from any value to a boolean, and applies that function to every element of a given list, keeping only those elements for which the function returns True on. The function that List.f...

def multiply(factor: Int)(numberToBeMultiplied: Int): Int = factor * numberToBeMultiplied val multiplyBy3 = multiply(3)_ // resulting function signature Int => Int val multiplyBy10 = multiply(10)_ // resulting function signature Int => Int val sixFromCurriedCall = multiplyBy3(2) //6...

def numberOrCharacterSwitch(toggleNumber: Boolean)(number: Int)(character: Char): String = if (toggleNumber) number.toString else character.toString // need to explicitly specify the type of the parameter to be curried // resulting function signature Boolean => String val switchBetween3A...

def minus(left: Int, right: Int) = left - right val numberMinus5 = minus(_: Int, 5) val fiveMinusNumber = minus(5, _: Int) numberMinus5(7) // 2 fiveMinusNumber(7) // -2

Some JavaScript engines (for example, the current version of Node.js and older versions of Chrome before Ignition+turbofan) don't run the optimizer on functions that contain a try/catch block. If you need to handle exceptions in performance-critical code, it can be faster in some cases to keep the ...

Flask lets you use templates for dynamic web page content. An example project structure for using templates is as follows: myproject/ /app/ /templates/ /index.html /views.py views.py: from flask import Flask, render_template app = Flask(__name__) @app...