Tutorial by Examples: nd

This is a huge topic, but it is also the most important "performance" issue. The main lesson for a novice is to learn of "composite" indexes. Here's a quick example: INDEX(last_name, first_name) is excellent for these: WHERE last_name = '...' WHERE first_name = '...' AND ...

Example below shows how to create a BroadcastReceiver which is able to receive BOOT_COMPLETED events. This way, you are able to start a Service or start an Activity as soon device was powered up. Also, you can use BOOT_COMPLETED events to restore your alarms since they are destroyed when device is ...

Having a global allows for better DRYness, you need only put values that are different into AssemblyInfo.cs for projects that have variance. This use assumes your product has more than one visual studio project. GlobalAssemblyInfo.cs using System.Reflection; using System.Runtime.InteropServices...

2.12.2 You can use the minElement() and maxElement() methods to find the minimum or maximum element in a given sequence. For example, with an array of numbers: let numbers = [2, 6, 1, 25, 13, 7, 9] let minimumNumber = numbers.minElement() // Optional(1) let maximumNumber = numbers.maxElement()...

Sometimes you may need to validate record only under certain conditions. class User < ApplicationRecord validates :name, presence: true, if: :admin? def admin? conditional here that returns boolean value end end If you conditional is really small, you can use a Proc: class ...

In PHP, there are two versions of logical AND and OR operators. OperatorTrue if$a and $bBoth $a and $b are true$a && $bBoth $a and $b are true$a or $bEither $a or $b is true$a || $bEither $a or $b is true Note that the && and || opererators have higher precedence than and and or. S...

As with docopt, with [docopt_dispatch] you craft your --help in the __doc__ variable of your entry-point module. There, you call dispatch with the doc string as argument, so it can run the parser over it. That being done, instead of handling manually the arguments (which usually ends up in a high c...

Manually open and close a file. # Using new method f = File.new("test.txt", "r") # reading f = File.new("test.txt", "w") # writing f = File.new("test.txt", "a") # appending # Using open method f = open("test.txt", "r&...

The Chef documentation can be found at https://docs.chef.io/

General syntax: DATEADD (datepart , number , datetime_expr) To add a time measure, the number must be positive. To subtract a time measure, the number must be negative. Examples DECLARE @now DATETIME2 = GETDATE(); SELECT @now; --2016-07-21 14:39:46.4170000 SELECT DAT...

Sometimes when destructuring maps, you would like to bind the destructured values to their respective key name. Depending on the granularity of the data structure, using the standard destructuring scheme may be a little bit verbose. Let's say, we have a map based record like so : (def john {:lastn...

A CSS rule consists of a selector (e.g. h1) and declaration block ({}). h1 {}

Make sure your tomcat configurations file, server.xml has this line: <Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol" maxHttpHeaderSize="8192" SSLEnabled="true" maxThreads="150" minSpareThrea...

A common refrain in R goes along these lines: You should not have a bunch of related tables with names like DT1, DT2, ..., DT11. Iteratively reading and assigning to objects by name is messy. The solution is a list of tables of data! Such a list looks like set.seed(1) DT_list = lapply(setNam...

PMF FOR THE BINOMIAL DISTRIBUTION Suppose that a fair die is rolled 10 times. What is the probability of throwing exactly two sixes? You can answer the question using the dbinom function: > dbinom(2, 10, 1/6) [1] 0.29071 PMF FOR THE POISSON DISTRIBUTION The number of sandwhich ordered in ...

Knitr is an R package that allows us to intermingle R code with LaTeX code. One way to achieve this is external code chunks. External code chunks allow us to develop/test R Scripts in an R development environment and then include the results in a report. It is a powerful organizational technique....

We try to extract imdb top chart movies and ratings R> library(RCurl) R> library(XML) R> url <- "http://www.imdb.com/chart/top" R> top <- getURL(url) R> parsed_top <- htmlParse(top, encoding = "UTF-8") R> top_table <- readHTMLTable(parsed_top)[...

First thing to do is enable the mod rewrite on wamp go to Apache modules and scroll down the list If not showing tick enable it and then restart all servers. Linux users can also use below terminal command to enable rewrite module sudo a2enmod rewrite Then restart apache using: sudo service...

Chaining and Chainable is a design methodology used to design object behaviors so that calls to object functions return references to self, or another object, providing access to additional function calls allowing the calling statement to chain together many calls without the need to reference the v...

Paste your fonts file inside android/app/src/main/assets/fonts/font_name.ttf Recompile the Android app by running react-native run-android Now, You can use fontFamily: 'font_name' in your React Native Styles