Tutorial by Examples: d

Selecting with Condition

The basic syntax of SELECT with WHERE clause is: SELECT column1, column2, columnN FROM table_name WHERE [condition] The [condition] can be any SQL expression, specified using comparison or logical operators like >, <, =, <>, >=, <=, LIKE, NOT, IN, BETWEEN etc. The following ...
SQL • SELECT

Select Individual Columns

SELECT PhoneNumber, Email, PreferredContact FROM Customers This statement will return the columns PhoneNumber, Email, and PreferredContact from all rows of the Customers table. Also the columns will be returned in the sequence in which they appear in the SELECT clause. The re...
SQL • SELECT

Introduction

Definition: In computing, an event is an action or occurrence recognized by software that may be handled by the software. Computer events can be generated or triggered by the system, by the user or in other ways. Definition Source HTML events are "things" that happen to HTML ele...
DOM • Events

Waiting for the document to load

One of the most commonly used events is waiting for the document to have loaded, including both script files and images. The load event on document is used for this. document.addEventListener('load', function() { console.log("Everything has now loaded!"); }); Sometimes you try to ...
DOM • Events

Setting Default Values

By default, attempting to lookup the value for a key which does not exist will return nil. You can optionally specify some other value to return (or an action to take) when the hash is accessed with a non-existent key. Although this is referred to as "the default value", it need not be a s...

Null and Undefined

The differences between null and undefined null and undefined share abstract equality == but not strict equality ===, null == undefined // true null === undefined // false They represent slightly different things: undefined represents the absence of a value, such as before an identifier/...

`load` vs `loads`, `dump` vs `dumps`

The json module contains functions for both reading and writing to and from unicode strings, and reading and writing to and from files. These are differentiated by a trailing s in the function name. In these examples we use a StringIO object, but the same functions would apply for any file-like obje...

Sending objects to a generator

In addition to receiving values from a generator, it is possible to send an object to a generator using the send() method. def accumulator(): total = 0 value = None while True: # receive sent value value = yield total if value is None: break # aggr...

Introduction

Generator expressions are similar to list, dictionary and set comprehensions, but are enclosed with parentheses. The parentheses do not have to be present when they are used as the sole argument for a function call. expression = (x**2 for x in range(10)) This example generates the 10 first perfe...

Get Started

Download Xcode from the Mac App Store. Click to create a new project or playground:

Getting Started

Create a new HTML file and paste the following content: <!DOCTYPE html> <html ng-app> <head> <title>Hello, Angular</title> <script src="https://code.angularjs.org/1.5.8/angular.min.js"></script> </head> <body ng-init="name=...

Background Color

The background-color property sets the background color of an element using a color value or through keywords, such as transparent, inherit or initial. transparent, specifies that the background color should be transparent. This is default. inherit, inherits this property from its parent e...

Extract the URLs and titles of links

Jsoup can be be used to easily extract all links from a webpage. In this case, we can use Jsoup to extract only specific links we want, here, ones in a h3 header on a page. We can also get the text of the links. Document doc = Jsoup.connect("http://stackoverflow.com").userAgent("Mozi...

Addition

a, b = 1, 2 # Using the "+" operator: a + b # = 3 # Using the "in-place" "+=" operator to add and assign: a += b # a = 3 (equivalent to a = a + b) import operator # contains 2 argument arithmetic functions for the examp...

Hello World Using Variables

Create a new file called hello.sh with the following content and give it executable permissions with chmod +x hello.sh. Execute/Run via: ./hello.sh #!/usr/bin/env bash # Note that spaces cannot be used around the `=` assignment operator whom_variable="World" # Use printf to sa...

Getting Started

Creating a database in MySQL CREATE DATABASE mydb; Return value: Query OK, 1 row affected (0.05 sec) Using the created database mydb USE mydb; Return value: Database Changed Creating a table in MySQL CREATE TABLE mytable ( id int unsigned NOT NULL auto_increme...

Division

Python does integer division when both operands are integers. The behavior of Python's division operators have changed from Python 2.x and 3.x (see also Integer Division ). a, b, c, d, e = 3, 2, 2.0, -3, 10 Python 2.x2.7 In Python 2 the result of the ' / ' operator depends on the type of the nu...

Rounding

Rounding Math.round() will round the value to the closest integer using half round up to break ties. var a = Math.round(2.3); // a is now 2 var b = Math.round(2.7); // b is now 3 var c = Math.round(2.5); // c is now 3 But var c = Math.round(-2.7); // c is now -3 va...

Using a generator to find Fibonacci Numbers

A practical use case of a generator is to iterate through values of an infinite series. Here's an example of finding the first ten terms of the Fibonacci Sequence. def fib(a=0, b=1): """Generator that yields Fibonacci numbers. `a` and `b` are the seed values""" ...

Hidden

<input type="hidden" name="inputName" value="inputValue"> A hidden input won't be visible to the user, but its value will be sent to the server when the form is submitted nonetheless.

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