Connect MySQL Remotely, Amazon EC2 using MySQL Workbench

Login to AWS Management Console. Under the security group, add inbound rule for MySQL.

First login to EC2 instance using SSH, then login to mysql 

mysql -hlocalhost -uroot -p

provide the password. Once you are in mysql prompt

CREATE USER 'testuser'@'%' IDENTIFIED BY 'testpwd'

GRANT ALL PRIVILEGES ON *.* TO 'testuser'@'%' WITH GRANT OPTION

FLUSH PRIVILEGES

Note: Setting host to '%' may be harmful, you can set your IP address to access the MySQL from your IP address only

Now open the my.cnf file from /etc/mysql and search for bind-address, the default value will be

bind-address = 127.0.0.1

change it to

 bind-address = 0.0.0.0

That's it now go to MySQL workbench, create connection with

Host:

Username: testuser

 

MySQL Simple JOINS

Simple Example: Lets say you have a Students table, and a Lockers table. Each student can be assigned to a locker, so there is a "Locker Number" column in the student table. More than one student could potentially be in a single locker, but especially at the beginning of the school year, you may have some incoming students without lockers and some lockers that have no students assigned. For the sake of this example, lets say you have 100 students, 70 of which have lockers. You have a total of 50 lockers, 40 of which have at least 1 student and 10 lockers have no student. INNER JOIN is equivalent to "show me all students with lockers". Any students without lockers, or any lockers without students are missing. Returns 70 rows LEFT OUTER JOIN would be "show me all students, with their corresponding locker if they have one". This might be a general student list, or could be used to identify students with no locker. Returns 100 rows RIGHT OUTER JOIN would be "show me all lockers, and the students assigned to them if there are any". This could be used to identify lockers that have no students assigned, or lockers that have too many students. Returns 80 rows (list of 70 students in the 40 lockers, plus the 10 lockers with no student) FULL OUTER JOIN would be silly and probably not much use. Something like "show me all students and all lockers, and match them up where you can" Returns 110 rows (all 100 students, including those without lockers. Plus the 10 lockers with no student) CROSS JOIN is also fairly silly in this scenario. It doesn't use the linked "locker number" field in the students table, so you basically end up with a big giant list of every possible student-to-locker pairing, whether or not it actually exists. Returns 5000 rows (100 students x 50 lockers). Could be useful (with filtering) as a starting point to match up the new students with the empty lockers. Original here

Find relative duration of an event using PHP for given date time (seconds ago, minutes ago, hours ago, days ago, weeks ago, months ago, years ago)

You might have seen that many of the live applications shows the time relative to when it was posted as seconds ago, minutes ago, hours ago, days ago, weeks ago, month ago, year ago and so on. Instead of showing the whole date and time of any possible action on the application it is shown with smaller units, more simpler ones like a minute ago, 15 minutes and 10 seconds ago etc. Here is how we achieve it using PHP, below are two methods that can be used, it requires a Date Time string in YYYY-MM-DD HH:II:SS format.


Method One:

  /**
     * returns the time ago in string
     * @param string $date_time
     *
     * @return string
     */
    function timeAgo($date_time)
    {
        $time_ago = strtotime($date_time);
        $cur_time = time();
        $time_elapsed = $cur_time - $time_ago;
        $seconds = $time_elapsed;
        $minutes = round($time_elapsed / 60);
        $hours = round($time_elapsed / 3600);
        $days = round($time_elapsed / 86400);
        $weeks = round($time_elapsed / 604800);
        $months = round($time_elapsed / 2600640);
        $years = round($time_elapsed / 31207680);
        $str = ''; // Seconds
        if ($seconds <= 60) {
            $str = "few seconds ago";
        } // Minuteselse
        if ($minutes <= 60) {
            if ($minutes == 1) {
                $str = "one minute ago";
            } else {
                $str = "$minutes minutes ago";
            }
        } // Hours
        else if ($hours <= 24) {
            if ($hours == 1) {
                $str = "an hour ago";
            } else {
                $str = "$hours hours ago";
            }
        } // Days
        else if ($days <= 7) {
            if ($days == 1) {
                $str = "yesterday";
            } else {
                $str = "$days days ago";
            }
        } // Weeks
        else if ($weeks <= 4.3) {
            if ($weeks == 1) {
                $str = "a week ago";
            } else {
                $str = "$weeks weeks ago";
            }
        } // Months
        else if ($months <= 12) {
            if ($months == 1) {
                $str = "a month ago";
            } else {
                $str = "$months months ago";
            }
        } // Years
        else {
            if ($years == 1) {
                $str = "one year ago";
            } else {
                $str = "$years years ago";
            }
        }
        return $str;
    }

ex:

echo timeAgo('2015-01-17 14:20:00'); 

o/p: 31 minutes ago

Method Two: in detail

  /**
     * gives time ago in detailed
     *
     * @param string $date_time
     * @return string
     */
    function timeAgo($date_time)
    {
        $then = new DateTime($date_time);
        $now = new DateTime();
        $delta = $now->diff($then);
        $quantities = array(
            'year' => $delta->y,
            'month' => $delta->m,
            'day' => $delta->d,
            'hour' => $delta->h,
            'minute' => $delta->i,
            'second' => $delta->s
        );
        $str = '';
        foreach ($quantities as $unit => $value) {
            if ($value == 0)
                continue;
            $str .= $value . ' ' . $unit;
            if ($value != 1) {
                $str .= 's';
            }
            $str .= ', ';
        }
        $str = $str == '' ? 'a moment ' : substr($str, 0, - 2);
        return $str . ' ago';
    }
    

ex:

echo timeAgo('2015-01-17 14:20:00'); 

o/p: 31 minutes, 14 seconds ago