Database stores all the information and data for your site so emphasize on related security.

Change the WordPress database table prefix:

Use of default prefix for wp- table makes the site database open to SQL injection use. It is possible to prevent this attack by using some other term for wp-.

Backup your site regularly:

With backup, restoring the WP site to working state is easy. Take help from plug-ins for the purpose.

Set strong passwords for your database:

Use special characters, lowercase, uppercase, and numbers for passwords.