How to find out how many identical records there are in a table?

Question

MySQL

Good evening!
I have a staff table with the following entries:

id  name         phone
1    Igor          [phone]
2    Alex           9637677676
3    Andrey        [phone]
4    Andrey         9655674587
5    Igor           9098987856
6    Ivan           9057688787

the table shows that there are numbers that repeat the last 10 characters, you need to understand how many such numbers are in the database.
How to make a request?

Answer 1

SELECT COUNT(*)
FROM (
  SELECT RIGHT(`phone`, 10) AS `p_number`, COUNT(*) AS `p_number_count`
  FROM `contacts`
  GROUP BY `p_number`
  HAVING `p_number_count` > 1
) AS `dupl_p_numbers`

Answer 2

SELECT DISTINCT RIGHT(phone, 10) FROM staff;
sqlfiddle.com/#!9/fd862/7