Laravel's database query builder provides a convenient, fluent interface to creating and running database queries.
- It uses PDO parameter binding to protect your application against SQL injection. There is no need to clean strings passed as bindings.

Joins

To perform a basic "inner join", you may use the join() method on a query builder instance.
The first argument is the name of the table you need to join to; the remaining arguments specify the relation of the columns for the join.
- You can join to multiple tables in a single query:
$users = DB::table('users')
 ->join('contacts', 'users.id', '=', 'contacts.user_id')
 ->join('orders', 'users.id', '=', 'orders.user_id')
 ->select('users.*', 'contacts.email', 'orders.price')
->get();
- To perform a "left join" query, use the leftJoin() method, in the same way as the join() method.
$users = DB::table('users')
 ->leftJoin('posts', 'users.id', '=', 'posts.user_id')
->get();

Unions

To "union" two queries together, create an initial query and use the union() method to union it with a second query.
$first = DB::table('users')->whereNull('first_name');

$users = DB::table('users')->whereNull('last_name')
->union($first)->get();


- Documentation: Laravel - Database: Query Builder

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which HTML5 tag defines marked text? (can be used to highlight parts of text)
<mark> <embed> <span>
<p>Free corses: <mark>coursesweb.net</mark> for Web Development.</p>
Which CSS pseudo-class adds a style to an element when the mouse is over it?
:focus :hover :active
a:hover {
  font-weight: bold;
  color: #00da01;
}
Click on the function which returns a string value that represents the number rounded to the x digits after the decimal point.
toPrecision(x) toFixed(x) floor(x)
var num = 12.34567;
num = num.toFixed(2);
alert(num);       // 12.35
Indicate the PHP function which reads an entire file into an array.
[) file() readfile()
$arr = file("a_file.txt", FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
var_export($arr);
MySQL Database, Query Builder: Join and Union

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