Tutorial by Examples: ect

Consider a database with the following two tables. Employees table: IdFNameLNameDeptId1JamesSmith32JohnJohnson4 Departments table: IdName1Sales2Marketing3Finance4IT Simple select statement * is the wildcard character used to select all available columns in a table. When used as a substitute f...

Normally, enums can't be recursive (because they would require infinite storage): enum Tree<T> { case leaf(T) case branch(Tree<T>, Tree<T>) // error: recursive enum 'Tree<T>' is not marked 'indirect' } The indirect keyword makes the enum store its payload with...

Standard Creation It is recommended to use this form only when creating regex from dynamic variables. Use when the expression may change or the expression is user generated. var re = new RegExp(".*"); With flags: var re = new RegExp(".*", "gmi"); With a backsl...

You can make Git ignore certain files and directories — that is, exclude them from being tracked by Git — by creating one or more .gitignore files in your repository. In software projects, .gitignore typically contains a listing of files and/or directories that are generated during the build proces...

The <select> element generates a drop-down menu from which the user can choose an option. <select name=""> <option value="1">One</option> <option value="2">Two</option> <option value="3">Three</option> ...

Since PHP 5.0, PDO has been available as a database access layer. It is database agnostic, and so the following connection example code should work for any of its supported databases simply by changing the DSN. // First, create the database handle //Using MySQL (connection via local socket): $d...

The basic syntax of SELECT with WHERE clause is: SELECT column1, column2, columnN FROM table_name WHERE [condition] The [condition] can be any SQL expression, specified using comparison or logical operators like >, <, =, <>, >=, <=, LIKE, NOT, IN, BETWEEN etc. The following ...

SELECT PhoneNumber, Email, PreferredContact FROM Customers This statement will return the columns PhoneNumber, Email, and PreferredContact from all rows of the Customers table. Also the columns will be returned in the sequence in which they appear in the SELECT clause. The re...

You can use slices to very easily reverse a str, list, or tuple (or basically any collection object that implements slicing with the step parameter). Here is an example of reversing a string, although this applies equally to the other types listed above: s = 'reverse me!' s[::-1] # '!em esrever...

In addition to receiving values from a generator, it is possible to send an object to a generator using the send() method. def accumulator(): total = 0 value = None while True: # receive sent value value = yield total if value is None: break # aggr...

This example show how to subscribe, and once that is successful, publishing a message to that channel. It also demonstrates the full set of parameters that can be included in the subscribe's message callback function. pubnub = PUBNUB({ publish_key : 'your_pub_key', ...

Xcode projects are used to organize source files, library dependencies, and other resources, as well as the settings and steps required to build the project's products. Workspaces are groups of projects and other files. Create a project You can create a New Project (⇧⌘N) from a number of built-in ...

Click the Run button in the toolbar (or press ⌘R) to build & run your project. Click Stop (or press ⌘.) to stop execution.   Click & hold to see the other actions, Test (⌘U), Profile (⌘I), and Analyze (⇧⌘B). Hold down modifier keys ⌥ option, ⇧ shift, and ⌃ control for more variants.  ...

Sorted sequences allow the use of faster searching algorithms: bisect.bisect_left()1: import bisect def index_sorted(sorted_seq, value): """Locate the leftmost value exactly equal to x or raise a ValueError""" i = bisect.bisect_left(sorted_seq, value) ...

int i = 42; i = i++; /* Assignment changes variable, post-increment as well */ int a = i++ + i--; Code like this often leads to speculations about the "resulting value" of i. Rather than specifying an outcome, however, the C standards specify that evaluating such an expression produc...

To access the event object, include an event parameter in the event listener callback function: var foo = document.getElementById("foo"); foo.addEventListener("click", onClick); function onClick(event) { // the `event` parameter is the event object // e.g. `event.type`...

The filter() method accepts a test function, and returns a new array containing only the elements of the original array that pass the test provided. // Suppose we want to get all odd number in an array: var numbers = [5, 32, 43, 4]; 5.1 var odd = numbers.filter(function(n) { return n % 2 !=...

Column aliases are used mainly to shorten code and make column names more readable. Code becomes shorter as long table names and unnecessary identification of columns (e.g., there may be 2 IDs in the table, but only one is used in the statement) can be avoided. Along with table aliases this allows ...

NaN ("Not a Number") is a special value defined by the IEEE Standard for Floating-Point Arithmetic, which is used when a non-numeric value is provided but a number is expected (1 * "two"), or when a calculation doesn't have a valid number result (Math.sqrt(-1)). Any equality or ...

Usually, you have to use git add or git rm to add changes to the index before you can git commit them. Pass the -a or --all option to automatically add every change (to tracked files) to the index, including removals: git commit -a If you would like to also add a commit message you would do: g...