SP 2013 Get user name from email address stored in database

I have created business process in SharePoint 2013

I have stored multiple user email address in different stages of a request to send email notifications.

I am storing these email address with request status and action user.

Now I want to display the user name instead of email address in the grid like this request is pending with which user I have tried using user profile but don't know how I can use it to display user name form the email address.

login user name I know how to display but wanted to write a method so if I pass an email address it will return me the user name.

can anyone guide me how can I do this.

I am storing all the information in SQL table and showing as report all the pending request in a grid.

so when user select the request status like pending with any role it gives me the list of all the request but there in the grid column I want to show the user name instead of email address.

Thanks