Tutorial by Examples: t

Table creation with Foreign Key

CREATE TABLE Account ( AccountID INT UNSIGNED NOT NULL, AccountNo INT UNSIGNED NOT NULL, PersonID INT UNSIGNED, PRIMARY KEY (AccountID), FOREIGN KEY (PersonID) REFERENCES Person (PersonID) ) ENGINE=InnoDB; Foreign key: A Foreign Key (FK) is either a single col...

MySQL • Table Creation

Installation or Setup

Detailed instructions on getting pandas set up or installed can be found here in the official documentation. Installing pandas with Anaconda Installing pandas and the rest of the NumPy and SciPy stack can be a little difficult for inexperienced users. The simplest way to install not only pandas, ...

pandas • Getting started with pandas

Installation or Setup

ReactJS is a JavaScript library contained in a single file react-<version>.js that can be included in any HTML page. People also commonly install the React DOM library react-dom-<version>.js along with the main React file: Basic Inclusion <!DOCTYPE html> <html> <...

React • Getting started with React

Arrays to Stream

Java SE 8 Converting an array of objects to Stream: String[] arr = new String[] {"str1", "str2", "str3"}; Stream<String> stream = Arrays.stream(arr); Converting an array of primitives to Stream using Arrays.stream() will transform the array to a primitive sp...

Java Language • Arrays

Create an XML file using XMLWriter

Instantiate a XMLWriter object: $xml = new XMLWriter(); Next open the file to which you want to write. For example, to write to /var/www/example.com/xml/output.xml, use: $xml->openUri('file:///var/www/example.com/xml/output.xml'); To start the document (create the XML open tag): $xml-&gt...

PHP • XML

Show both staged and unstaged changes

To show all staged and unstaged changes, use: git diff HEAD NOTE: You can also use the following command: git status -vv The difference being that the output of the latter will actually tell you which changes are staged for commit and which are not.

Git • Git Diff

Installation or Setup

Knockout is available on most JavaScript platforms, or as a standalone script. Include as a script You can download the script from it's download page, then include it in your page with a standard script tag <script type='text/javascript' src='knockout-3.4.0.js'></script> Using a C...

knockout.js • Getting started with knockout.js

Clearing an activity stack

Sometimes you may want to start a new activity while removing previous activities from the back stack, so the back button doesn't take you back to them. One example of this might be starting an app on the Login activity, taking you through to the Main activity of your application, but on logging out...

Android • Intent

Linear regression on the mtcars dataset

The built-in mtcars data frame contains information about 32 cars, including their weight, fuel efficiency (in miles-per-gallon), speed, etc. (To find out more about the dataset, use help(mtcars)). If we are interested in the relationship between fuel efficiency (mpg) and weight (wt) we may start p...

R Language • Linear Models (Regression)

Use anonymous functions with apply

apply is used to evaluate a function (maybe an anonymous one) over the margins of an array or matrix. Let's use the iris dataset to illustrate this idea. The iris dataset has measurements of 150 flowers from 3 species. Let's see how this dataset is structured: > head(iris) Sepal.Length Sep...

R Language • *apply family of functions (functionals)

Cloning an existing table

A table can be replicated as follows: CREATE TABLE ClonedPersons LIKE Persons; The new table will have exactly the same structure as the original table, including indexes and column attributes. As well as manually creating a table, it is also possible to create table by selecting data from anot...

MySQL • Table Creation

Array definition

Dim array(9) As Integer ' Defines an array variable with 10 Integer elements (0-9). Dim array = New Integer(10) {} ' Defines an array variable with 11 Integer elements (0-10) 'using New. Dim array As Integer() = {1, 2, 3, 4} ' Defines an Integer array variable a...

Visual Basic .NET Language • Array

Enum Polymorphism Pattern

When a method need to accept an "extensible" set of enum values, the programmer can apply polymorphism like on a normal class by creating an interface which will be used anywere where the enums shall be used: public interface ExtensibleEnum { String name(); } This way, any enum t...

Java Language • Enums

Reversing Strings

2.2 let aString = "This is a test string." // first, reverse the String's characters let reversedCharacters = aString.characters.reverse() // then convert back to a String with the String() initializer let reversedString = String(reversedCharacters) print(reversedString) // &q...

Swift Language • Strings and Characters

Adding the Doctype

The <!DOCTYPE> declaration should always be included at the top of the HTML document, before the <html> tag. 5 See HTML 5 Doctype for details on the HTML 5 Doctype. <!DOCTYPE html> 4.01 See HTML 4.01 Doctypes for details on how these types differ from each other. Stri...

HTML • Doctypes

Get the list of all databases on a server

Method 1: Below query will be applicable for SQL Server 2000+ version (Contains 12 columns) SELECT * FROM dbo.sysdatabases Method 2: Below query extract information about databases with more informations (ex: State, Isolation, recovery model etc.) Note: This is a catalog view and will be availa...

Microsoft SQL Server • Retrieve information about the database

Install Yii2 advanced in ubuntu

First we need to install composer. Steps to install composer Install Composer. curl -sS https://getcomposer.org/installer | php Now change directory: sudo mv composer.phar /usr/local/bin/composer Check composer working composer Now Composer installed. There two ways to install Yii2 adv...

yii2 • Getting started with yii2

Interfaces

Introduction Interfaces are definitions of the public APIs classes must implement to satisfy the interface. They work as "contracts", specifying what a set of subclasses does, but not how they do it. Interface definition is much alike class definition, changing the keyword class to inter...

PHP • Classes and Objects

Manipulating Array Elements

Adding elements: [1, 2, 3] << 4 # => [1, 2, 3, 4] [1, 2, 3].push(4) # => [1, 2, 3, 4] [1, 2, 3].unshift(4) # => [4, 1, 2, 3] [1, 2, 3] << [4, 5] # => [1, 2, 3, [4, 5]] Removing elements: array = [1, 2, 3, 4] array.pop # => 4 array # => [1, 2, 3] ...

Ruby Language • Arrays

while, until

A while loop executes the block while the given condition is met: i = 0 while i < 5 puts "Iteration ##{i}" i +=1 end An until loop executes the block while the conditional is false: i = 0 until i == 5 puts "Iteration ##{i}" i +=1 end

Ruby Language • Control Flow