Tutorial by Examples: l

There may be situations where you have setup a pool of MySQL connections, but you have a number of queries you would like to run in sequence: SELECT 1; SELECT 2; You could just run then using pool.query as seen elsewhere, however if you only have one free connection in the pool you must wait un...

0-1 Knapsack The Knapsack Problem is a problem when given a set of items, each with a weight, a value and exactly 1 copy, determine the which item(s) to include in a collection so that the total weight is less than or equal to a given limit and the total value is as large as possible. C++ Exampl...

Callback-based: db.notification.email.find({subject: 'promisify callback'}, (error, result) => { if (error) { console.log(error); } // normal code here }); This uses bluebird's promisifyAll method to promisify what is conventionally callback-based code like above. blueb...

A view is most useful when it can be used to pull in data from more than one table. CREATE VIEW myview AS SELECT a.*, b.extra_data FROM main_table a LEFT OUTER JOIN other_table b ON a.id = b.id In mysql views are not materialized. If you now perform the simple query SELECT * FROM myview, my...

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The most important application events are: Application_Start - It is raised when the application/website is started. Application_End - It is raised when the application/website is stopped. Similarly, the most used Session events are: Session_Start - It is raised when a user first requests a page...

Common page and control events are: DataBinding - It is raised when a control binds to a data source. Disposed - It is raised when the page or the control is released. Error - It is a page event, occurs when an unhandled exception is thrown. Init - It is raised when the page or the control is in...

The default event for the Page object is Load event. Similarly, every control has a default event. For example, default event for the button control is the Click event. The default event handler could be created in Visual Studio, just by double clicking the control in design view. The following tab...

You can use this method to replace all of the HTML within the selector. Assuming you have an html element like this <div class="row"> <div class="col-md-12"> <div id="information"> <p>Old message</p> &l...

PHP 5.x5.4 When you build REST API's, you may need to reduce the information of an object to be passed to the client application. For this purpose, this example illustrates how to use the JsonSerialiazble interface. In this example, the class User actually extends a DB model object of a hypotetica...

Laravel allows user work on multiple database connections. If you need to connect to multiple databases and make them work together, you are beware of the connection setup. You also allow using different types of database in the same application if you required. Default connection In config/dat...

[JsonObject("person")] public class Person { [JsonProperty("name")] public string PersonName { get; set; } [JsonProperty("age")] public int PersonAge { get; set; } [JsonIgnore] public string Address { get; set; } } Person person = new...

There are two common conventions for private fields: camelCase and _camelCaseWithLeadingUnderscore. Camel case public class Rational { private readonly int numerator; private readonly int denominator; public Rational(int numerator, int denominator) { // "this&q...

Remove all characters except digits, +- and optionally .,eE. var_dump(filter_var(1, FILTER_SANITIZE_NUMBER_FLOAT)); var_dump(filter_var(1.0, FILTER_SANITIZE_NUMBER_FLOAT)); var_dump(filter_var(1.0000, FILTER_SANITIZE_NUMBER_FLOAT)); var_dump(filter_var(1.00001, FILTER_SANITIZE_NUMBER_FLOAT)); v...

You've made a stash and wish to checkout only some of the files in that stash. git checkout stash@{0} -- myfile.txt

TCO is only available in strict mode As always check browser and Javascript implementations for support of any language features, and as with any javascript feature or syntax, it may change in the future. It provides a way to optimise recursive and deeply nested function calls by eliminating the n...

Tail Call Optimisation makes it possible to safely implement recursive loops without concern for call stack overflow or the overhead of a growing frame stack. function indexOf(array, predicate, i = 0) { if (0 <= i && i < array.length) { if (predicate(array[i])) { return...

Consider the following example assuming that you have a ';'-delimited CSV to load into your database. 1;max;male;manager;12-7-1985 2;jack;male;executive;21-8-1990 . . . 1000000;marta;female;accountant;15-6-1992 Create the table for insertion. CREATE TABLE `employee` ( `id` INT NOT NULL , ...

Syntax is: LEFT ( string-expression , integer ) RIGHT ( string-expression , integer ) SELECT LEFT('Hello',2) --return He SELECT RIGHT('Hello',2) --return lo Oracle SQL doesn't have LEFT and RIGHT functions. They can be emulated with SUBSTR and LENGTH.SUBSTR ( string-expression, 1, intege...

What if you want to rollback the latest migration i.e recent operation, you can use the awesome rollback command. But remember that this command rolls back only the last migration, which may include multiple migration files php artisan migrate:rollback If you are interested in rolling back all o...