How to find which emails are in the same lists?

Question

I have a 11 tables [email1, email2, email3, ... email11]

Answer 1

MySQL UNION operator allows you to combine two or more result sets from multiple tables into a single result set

SELECT Contact_Email FROM email1
UNION
SELECT Contact_Email FROM email2
UNION
SELECT Contact_Email FROM email3
.
.
UNION
SELECT Contact_Email FROM email11

By default, the UNION operator eliminates duplicate rows from the result even if you don’t use DISTINCT operator explicitly.