i had been searching that in which the wordpress save the URL/Link from the Avatar from the blog within the Database of wordpress anybody might help?
Wordpress uses Gravatar (Global Recognized Avatars -> see www.gravatar.com).
Gravatar relies upon the e-mail-address. So there's no concrete link inside the database to have an avatar. It's based on the posters E-Mail, which in turn is changed right into a gravatar-url inside the wordpress-code.
the avatar link isn't held in the database.
<img src="http://gravatar.com/avatar/your-emailadress-hashed-by-md5"> even Stack Overflow/Stack Exchange uses this.