SELECT * 
FROM `member` a 
join (SELECT password, count(password) as pw_count 
FROM `member`
group by password
HAVING COUNT(password) > 1) b on b.password = a.password

Find members that have the same password

More Advanced – Get minimum member ID from members that have same password:

SELECT min(a.id) as m_id, b.pw_count
FROM `member` a 
join (SELECT password, count(password) as pw_count 
FROM `member`
group by password
HAVING COUNT(password) > 1) b on b.password = a.password
group by b.pw_count

 

Reference:

• http://www.mysql.tw/2014/06/sqlwherehaving.html
• https://stackoverflow.com/questions/9803004/mysql-group-by-with-where-clause-with-having-count-greater-than-1