WordPress Database is like a brain for your entire WordPress site because every single information is stored in there thus making it hacker’s favorite target. Spammers and hackers run automated codes for SQL injections. Well, unfortunately many people forget to change the database prefix while they install WordPress. This makes it easier for hackers to plan a mass attack by targeting the default prefix wp_. The smartest way you can protect your database is by changing the database prefix which is really easy to do on a site that you are setting up. But it takes a few steps to change the WordPress database prefix properly for your established site without completely messing it up.

We recommend that you backup your WordPress Database before you perform anything suggested in this tutorial. It is important to keep daily backups of your site, we recommend BackupBuddy plugin for doing that. Next thing we recommend is that you redirect your visitors to a temporary maintenance page.
Change Table Prefix in wp-config.php

Open your wp-config.php file which is located in your WordPress root directory. Change the table prefix line from wp_ to something else like this wp_a123456_

So the line would look like this:

$table_prefix = ‘wp_a123456_’;

Note: You can only change it to numbers, letters, and underscores.
Change all Database Tables Name