MySql snippets

query dupicate.sql

select 
    nickname, count(id) as cnt 
from 
    customer
group by
    nickname having cnt > 1

update duplicate.sql

update login a,
       (select a.id
        from   login a,
               (select   email, count(id) as num
                from     login
                group by email
                having   count(id) >= 2) b
        where  a.email = b.email) b
set    a.email = concat(a.id, '@old-email.local')
where  a.id = b.id