Loop though the list which is retrieved from database
Inside loop, retrieve from database using the following xpath
If the object is empty, then Mobile Number is unique
If the object is not empty, then Mobile Number already exists
Hope it helps!!!
I don't think you need to use a count action here. You can use a database retrieve on Employee where you check the following things:
[Mobilenumber = $employee/Mobilenumber]
[id !_ $employee/id]
This way you can check if the mobile number is already used for another employee.
Hope this helps!