Tutorial by Examples: e

Common Lisp does not have interfaces in the sense that some languages (e.g., Java) do, and there is less need for that type of interface given that Common Lisp supports multiple inheritance and generic functions. However, the same type of patterns can be realized easily using mixin classes. This e...

Let's say we have a table team_person as below: +======+===========+ | team | person | +======+===========+ | A | John | +------+-----------+ | B | Smith | +------+-----------+ | A | Walter | +------+-----------+ | A | Louis | +------+-----------+ | C | ...

The unreal mode exploits two facts on how both Intel and AMD processors load and save the information to describe a segment. The processor caches the descriptor information fetched during a move in a selector register in protected mode. These information are stored in an architectural invisibl...

RENAME TABLE t TO t_old, t_copy TO t; No other sessions can access the tables involved while RENAME TABLE executes, so the rename operation is not subject to concurrency problems. Atomic Rename is especially for completely reloading a table without waiting for DELETE and load to finish: CREATE ...

A VIEW acts very much like a table. Although you can UPDATE a table, you may or may not be able to update a view into that table. In general, if the SELECT in the view is complex enough to require a temp table, then UPDATE is not allowed. Things like GROUP BY, UNION, HAVING, DISTINCT, and some su...

To run the software: After the download of the platform-independent ZIP file completes, extract it to any folder on your system. Run the executable file located in the netbeans/bin directory. Accept the License Agreement. Click Next. The NetBeans IDE installation starts. Note: If a compatib...

PHP 5.4+ comes with a built-in development server. It can be used to run applications without having to install a production HTTP server such as nginx or Apache. The built-in server is only designed to be used for development and testing purposes. It can be started by using the -S flag: php -S &lt...

The ROLLUP operator is useful in generating reports that contain subtotals and totals. CUBE generates a result set that shows aggregates for all combinations of values in the selected columns. ROLLUP generates a result set that shows aggregates for a hierarchy of values in the selected col...

R contains a Date class, which is created with as.Date(), which takes a string or vector of strings, and if the date is not in ISO 8601 date format YYYY-MM-DD, a formatting string of strptime-style tokens. as.Date('2016-08-01') # in ISO format, so does not require formatting string ## [1] &quot...

Sometimes you will create classes that won't be used in their own right, rather only be extended inside other rule sets. This means that the compiled CSS file will be larger than it needs to be. Placeholder selectors solve this problem. Placeholder selectors are similar to class selectors, but th...

The most important thing for speeding up a query on any non-tiny table is to have a suitable index. WHERE a = 12 --> INDEX(a) WHERE a > 12 --> INDEX(a) WHERE a = 12 AND b > 78 --> INDEX(a,b) is more useful than INDEX(b,a) WHERE a > 12 AND b > 78 --> INDEX(a) or INDE...

A common mistake is to hide an indexed column inside a function call. For example, this can't be helped by an index: WHERE DATE(dt) = '2000-01-01' Instead, given INDEX(dt) then these may use the index: WHERE dt = '2000-01-01' -- if `dt` is datatype `DATE` This works for DATE, DATETIME, TIM...

Subqueries come in several flavors, and they have different optimization potential. First, note that subqueries can be either "correlated" or "uncorrelated". Correlated means that they depend on some value from outside the subquery. This generally implies that the subquery mus...

Create a testing class in the src/test/scala directory, in a file named HelloWorldSpec.scala. Put this inside the file: import org.scalatest.{FlatSpec, Matchers} class HelloWorldSpec extends FlatSpec with Matchers { "Hello World" should "not be an empty String" in { ...

Detailed instructions on getting cloudkit set up or installed.

import { NgModule } from '@angular/core'; @NgModule({ declarations: [], // components your module owns. imports: [], // other modules your module needs. providers: [], // providers available to your module. bootstrap: [] // bootstrap this root component. }) export class MyModule {} ...

// app.module.ts import { NgModule } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { HttpModule } from '@angular/http'; import { MyRootComponent } from './app.component'; @NgModule({ declarations: [MyRootComponent], imports: [BrowserModule, Ht...

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'; import { MyModule } from './app.module'; platformBrowserDynamic().bootstrapModule( MyModule ); In this example, MyModule is the module containing your root component. By bootstrapping MyModule your Angul...

This example has two parts - some boilerplate steps for adding Castle Windsor to your WCF service, and then a simple, concrete example to show how we configure and use Windsor's container. That makes the example a little bit long. If you already understand using a DI container then you likely only ...

Helper yii\helpers\Url provides a set of static methods for managing URLs. This helper may used in views/controllers code. URL to a route: echo Url::to(['post/index']); URL to a route with parameters: echo Url::to(['post/view', 'id' => 100]); anchored URL: echo Url::to(['post/view', 'id...