Tutorial by Examples: n

Because the WHERE clause is evaluated before GROUP BY, you cannot use WHERE to pare down results of the grouping (typically an aggregate function, such as COUNT(*)). To meet this need, the HAVING clause can be used. For example, using the following data: DECLARE @orders TABLE(OrderID INT, Name NVA...

It is sometimes required for a process to concurrently write and read the same "data". The ReadWriteLock interface, and its ReentrantReadWriteLock implementation allows for an access pattern that can be described as follow : There can be any number of concurrent readers of the data. If...

Services declaration : # src/Acme/YourBundle/Resources/config/services.yml services: my_service: class: Acme\YourBundle\Service\MyService arguments: ["@doctrine", "%some_parameter%", "@another_service"] another_service: class: Ac...

It can be difficult to test functions with poor asymptotic complexity using quickcheck as the random inputs are not usually size bounded. By adding an upper bound on the size of the input we can still test these expensive functions. import Data.List(permutations) import Test.QuickCheck longRunn...

For an instance, if the html source code of an html view or element is wrapped by an iframe like this: <iframe src="../images/eightball.gif" name="imgboxName" id="imgboxId"> <p>iframes example</p> <a href="../images/redball.gif" t...

To switch focus to either main document or first frame of the page. You have to use below syntax. driver.switchTo().defaultContent();

el-get is an open source package management system for GNU Emacs. el-get works with melpa, as well as with many common version control systms. Its documentation includes a simple self-installer for your .emacs: (unless (require 'el-get nil t) (url-retrieve "https://raw.github.com/dim...

Function-like macros are similar to inline functions, these are useful in some cases, such as temporary debug log: #ifdef DEBUG # define LOGFILENAME "/tmp/logfile.log" # define LOG(str) do { \ FILE *fp = fopen(LOGFILENAME, "a"); \ ...

This attribute is applied to the class property. You can use ConcurrencyCheck attribute when you want to use existing columns for concurrency check and not a separate timestamp column for concurrency. using System.ComponentModel.DataAnnotations; public class Author { public int AuthorId { ...

Basically, parfor is recommended in two cases: lots of iterations in your loop (i.e., like 1e10), or if each iteration takes a very long time (e.g., eig(magic(1e4))). In the second case you might want to consider using spmd . The reason parfor is slower than a for loop for short ranges or fast itera...

We can create a Map from a list of tuples like this: Map.fromList [("Alex", 31), ("Bob", 22)] A Map can also be constructed with a single value: > Map.singleton "Alex" 31 fromList [("Alex",31)] There is also the empty function. empty :: Map k a ...

This time we are going to declare a class decorator that will add some metadata to a class when we applied to it: function addMetadata(target: any) { // Add some metadata target.__customMetadata = { someKey: "someValue" }; // Return target ret...

We can wrap a class decorator with another function to allow customization: function addMetadata(metadata: any) { return function log(target: any) { // Add metadata target.__customMetadata = metadata; // Return target return target; ...

The regular composition works for unary functions. In the case of binary, we can define (f .: g) x y = f (g x y) -- which is also = f ((g x) y) = (f . g x) y -- by definition of (.) = (f .) (g x) y = ((f .) . g) x y Thus,...

Extensions add new functionality to an existing class, structure, enumeration, or protocol type. This includes the ability to extend types for which you do not have access to the original source code. Extensions in Swift can: Add computed properties and computed type properties Define instance ...

In the Xcode, you have three separate areas of working - Navigators (in red), Debug area(in green) and Utilities(in blue). The workspace window always includes the editor area. When you select a file in your project, its contents appear in the editor area, where Xcode opens the file in an appropri...

PhpStorm can be very slow in large files as its performing so many inspections. One quick and easy way to speed up PhpStorm is to render using OpenGL. Previously in a 5000 line file it would give the 'eye' symbol in the top right for a long time before changing to a tick (or red/yellow box). After O...

Constructors are special methods named after the class and without a return type, and are used to construct objects. Constructors, like methods, can take input parameters. Constructors are used to initialize objects. Abstract classes can have constructors also. public class Hello{ // construct...

You can configure lint by adding a lintOptions section in the build.gradle file: android { //..... lintOptions { // turn off checking the given issue id's disable 'TypographyFractions','TypographyQuotes' // turn on the given issue id's enable 'Rtl...

You can specify your Lint checking preferences in the lint.xml file. If you are creating this file manually, place it in the root directory of your Android project. If you are configuring Lint preferences in Android Studio, the lint.xml file is automatically created and added to your Android project...