Tutorial by Examples: g

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MySQL does not provide a built-in way to create pivot queries. However, these can be created using prepared statements. Assume the table tbl_values: IdNameGroupValue1PeteA102PeteB203JohnA10 Request: Create a query that shows the sum of Value for each Name; the Group must be column header and Name...

1) Create a Contract Class A contract class defines constants that help applications work with the content URIs, column names, intent actions, and other features of a content provider. Contract classes are not included automatically with a provider; the provider's developer has to define them and t...

The primary way of getting input would be from injecting the Illuminate\Http\Request into your controller, after that there are numerous ways of accessing the data, 4 of which are in the example below. <?php namespace App\Http\Controllers; use Illuminate\Http\Request; class UserController...

globalize gem is a great solution to add translations to your ActiveRecord models. You can install it adding this to your Gemfile: gem 'globalize', '~> 5.0.0' If you're using Rails 5 you will also need to add activemodel-serializers-xml gem 'activemodel-serializers-xml' Model translations...

Due to type erasure the following will not work: public <T> void genericMethod() { T t = new T(); // Can not instantiate the type T. } The type T is erased. Since, at runtime, the JVM does not know what T originally was, it does not know which constructor to call. Workarounds ...

As with request bodies, HTTP responses may contain a message body. This provides additional data that the client will process. Notably, 200 OK responses to a well-formed GET request should always provide a message body containing the requested data. (If there is none, 204 No Content is a more approp...

A common problem is having a collection of items that all need to meet a certain criteria. In the example below we have collected two items for a diet plan and we want to check that the diet doesn't contain any unhealthy food. // First we create a collection $diet = collect([ ['name' => ...

You will often find yourself with a collection of data where you are only interested in parts of the data. In the example below we got a list of participants at an event and we want to provide a the tour guide with a simple list of names. // First we collect the participants $participants = colle...

Often you need to change the way a set of data is structured and manipulate certain values. In the example below we got a collection of books with an attached discount amount. But we much rather have a list of books with a price that's already discounted. $books = [ ['title' => 'The Pragma...

Collections also provide you with an easy way to do simple statistical calculations. $books = [ ['title' => 'The Pragmatic Programmer', 'price' => 20], ['title' => 'Continuous Delivery', 'price' => 30], ['title' => 'The Clean Coder', 'price' => 10], ] $min = col...

Functions are defined with five components: The header, which includes the defn keyword, the name of the function. (defn welcome ....) An optional Docstring that explains and document what the function does. (defn welcome "Return a welcome message to the world" ...) Pa...

Functions are objects in Julia. Like any other objects, they can be passed as arguments to other functions. Functions that accept functions are known as higher-order functions. For instance, we can implement an equivalent of the standard library's foreach function by taking a function f as the firs...

In Vue.js, every component instance has its own isolated scope, which means that if a parent component has a child component - the child component has its own isolated scope and the parent component has its own isolated scope. For any medium to large size app, following best practices conventions p...

Sometimes you will have a grid of subplots, and you want to have a single legend that describes all the lines for each of the subplots as in the following image. In order to do this, you will need to create a global legend for the figure instead of creating a legend at the axes level (which wil...

pacman is a simple package manager for R. pacman allows a user to compactly load all desired packages, installing any which are missing (and their dependencies), with a single command, p_load. pacman does not require the user to type quotation marks around a package name. Basic usage is as follows:...

Not always we have liberty to read from or write to a local system path. For example if R code streaming map-reduce must need to read and write to file connection. There can be other scenarios as well where one is going beyond local system and with advent of cloud and big data, this is becoming incr...

C++11 It's possible to write a generic function (for example min) which accepts various numerical types and arbitrary argument count by template meta-programming. This function declares a min for two arguments and recursively for more. template <typename T1, typename T2> auto min(const T1 &...

A variable can be downcasted to a subtype using the type cast operators as?, and as!. The as? operator attempts to cast to a subtype. It can fail, therefore it returns an optional. let value: Any = "John" let name = value as? String print(name) // prints Optional("John") ...

The switch statement can also be used to attempt casting into different types: func checkType(_ value: Any) -> String { switch value { // The `is` operator can be used to check a type case is Double: return "value is a Double" // The `as` operator will ...