Tutorial by Examples: in

Find nth highest salary using CTE

Microsoft SQL Server • Common Table Expressions

Delete duplicate rows using CTE

Microsoft SQL Server • Common Table Expressions

Creating a Simple VB.NET WinForms Application using a Text Editor

Open a text editor (like Notepad), and type the code below: Imports System.ComponentModel Imports System.Drawing Imports System.Windows.Forms Namespace SampleApp Public Class MainForm : Inherits Form Private btnHello As Button ' The form's constructor: thi...

winforms • Getting started with winforms

Cross Validation and Tuning with xgboost

library(caret) # for dummyVars library(RCurl) # download https data library(Metrics) # calculate errors library(xgboost) # model ############################################################################### # Load data from UCI Machine Learning Repository (http://archive.ics.uci.edu/ml/data...

R Language • xgboost

Benchmarking using microbenchmark

You can use the microbenchmark package to conduct "sub-millisecond accurate timing of expression evaluation". In this example we are comparing the speeds of six equivalent data.table expressions for updating elements in a group, based on a certain condition. More specifically: A data....

R Language • Code profiling

Overview of the basic path drawing commands: lines and curves

================== TODO: Link each of the drawing commands below to their individual examples. I don't know how to do this since the links to the individual examples point towards the "draft" folder. TODO: Add examples for these path "action" commands: stroke(), fill(), clip() ...

html5-canvas • Path (Syntax only)

lineTo (a path command)

context.lineTo(endX, endY) Draws a line segment from the current pen location to coordinate [endX,endY] <!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid red; } </style> <script> window.onload=(fun...

html5-canvas • Path (Syntax only)

beginPath (a path command)

context.beginPath() Begins assembling a new set of path commands and also discards any previously assembled path. It also moves the drawing "pen" to the top-left origin of the canvas (==coordinate[0,0]). Although optional, you should ALWAYS start a path with beginPath The discarding ...

html5-canvas • Path (Syntax only)

Installation or Setup

Linux Requirements (r0.16.0) Mandatory As per current Apache-Pig documentation it supports only Unix & Windows operating systems. Hadoop 0.23.X, 1.X or 2.X Java 1.6 or Later versions installed and JAVA_HOME environment variable set to Java installation directory Optional Python 2.7 ...

apache-pig • Getting started with apache-pig

Creating a Future

import scala.concurrent.Future import scala.concurrent.ExecutionContext.Implicits.global object FutureDivider { def divide(a: Int, b: Int): Future[Int] = Future { // Note that this is integer division. a / b } } Quite simply, the divide method creates a Future tha...

Scala Language • Futures

Consuming a Successful Future

The easiest way to consume a successful Future-- or rather, get the value inside the Future-- is to use the map method. Suppose some code calls the divide method of the FutureDivider object from the "Creating a Future" example. What would the code need to look like to get the quotient of...

Scala Language • Futures

Consuming a Failed Future

Sometimes the computation in a Future can create an exception, which will cause the Future to fail. In the "Creating a Future" example, what if the calling code passed 55 and 0 to the divide method? It'd throw an ArithmeticException after trying to divide by zero, of course. How would t...

Scala Language • Futures

Putting the Future Together

The previous examples demonstrated the individual features of a Future, handling success and failure cases. Usually, however, both features are handled much more tersely. Here's the example, written in a neater and more realistic way: object Calculator { def calculateAndReport(a: Int, b: Int...

Scala Language • Futures

Convert Exceptions into Either or Option Types

To convert exceptions into Either or Option types, you can use methods that provided in scala.util.control.Exception import scala.util.control.Exception._ val plain = "71a" val optionInt: Option[Int] = catching(classOf[java.lang.NumberFormatException]) opt { plain.toInt } val eitherI...

Scala Language • Error Handling

CROSS APPLY & LATERAL JOIN

A very interesting type of JOIN is the LATERAL JOIN (new in PostgreSQL 9.3+), which is also known as CROSS APPLY/OUTER APPLY in SQL-Server & Oracle. The basic idea is that a table-valued function (or inline subquery) gets applied for every row you join. This makes it possible to, for example...

SQL • JOIN

FULL JOIN

One type of JOIN that is less known, is the FULL JOIN. (Note: FULL JOIN is not supported by MySQL as per 2016) A FULL OUTER JOIN returns all rows from the left table, and all rows from the right table. If there are rows in the left table that do not have matches in the right table, or if there a...

SQL • JOIN

Recursive JOINs

Recursive joins are often used to obtain parent-child data. In SQL, they are implemented with recursive common table expressions, for example: WITH RECURSIVE MyDescendants AS ( SELECT Name FROM People WHERE Name = 'John Doe' UNION ALL SELECT People.Name FROM Peopl...

SQL • JOIN

ESCAPE statement in the LIKE-query

If you implement a text-search as LIKE-query, you usually do it like this: SELECT * FROM T_Whatever WHERE SomeField LIKE CONCAT('%', @in_SearchText, '%') However, (apart from the fact that you shouldn't necessarely use LIKE when you can use fulltext-search) this creates a problem when someb...

SQL • LIKE operator

Rebuild index

Over the course of time B-Tree indexes may become fragmented because of updating/deleting/inserting data. In SQLServer terminology we can have internal (index page which is half empty ) and external (logical page order doesn't correspond physical order). Rebuilding index is very similar to dropping...

SQL • Indexes

Finding the minimum or maximum element

If your array or array-like object is numeric, that is, if all its elements are numbers, then you can use Math.min.apply or Math.max.apply by passing null as the first argument, and your array as the second. var myArray = [1, 2, 3, 4]; Math.min.apply(null, myArray); // 1 Math.max.apply(null, my...

JavaScript • Arrays