Find rows that have the same value on a column in MySQL
In a [member] table, some rows have the same value for the email column.
login_id | email
---------|---------------------
john | [email protected]
peter | [email protected]
johnny | [email protected]
...
Some people used a different login_id but the same email address, no unique constraint was set on this column. Now I need to find these rows and see if they should be removed.
What SQL statement should I use to find these rows? (MySQL 5)
Answer
This query will give you a list of email addresses and how many times they're used, with the most used addresses first.
SELECT email,
count(*) AS c
FROM TABLE
GROUP BY email
HAVING c > 1
ORDER BY c DESC
If you want the full rows:
select * from table where email in (
select email from table
group by email having count(*) > 1
)