Unique Fields with the ability to be a reference to multiple records I wonder to know is it possible to have an unique field (let consider a text filed), when we input a data into it firstly it check the table if it doesn't exist add a record, if it find a record refer to it?

i.e.: I have a field in my content type to store telephone number whenever I want to add a new node, after entering the data into the telephone field if the number was stored in my database instead of creating a new record in the table I just reference to the number   

My aim is to have a contact list of some users that submit a form but I don't want duplication (just unique phone number and name)
I would envision this as 


Create a rule that post a node each time the form from anonymous user is submitted.
Create a condition before creating a node - the condition will loop through all entered node telephone numbers if they found that the user has already entered the data don't do anything other wise post the node with phone, name and email information.