Question

I need to count the number of duplicate emails in a mysql database, but without counting the first one (considered the original). In this table, the query result should be the single value “3” (2 duplicate [e-mail] plus 1 duplicate [e-mail]).

TABLE

ID | Name  | Email
1  | Mike  | [e-mail]
2  | Peter | [e-mail]
3  | Mike  | [e-mail]
4  | Mike  | [e-mail]
5  | Frank | [e-mail]
6  | Jim   | [e-mail]

My current query produces not one number, but multiple rows, one per email address regardless of how many duplicates of this email are in the table:

SELECT value, count(lds1.leadid) FROM leads_form_element lds1 LEFT JOIN leads lds2 ON lds1.leadID = lds2.leadID 
     WHERE lds2.typesID = "31" AND lds1.formElementID = '97'  
     GROUP BY lds1.value HAVING ( COUNT(lds1.value) > 1 )

Answer 1

It’s not one query so I’m not sure if it would work in your case, but you could do one query to select the total number of rows, a second query to select distinct email addresses, and subtract the two. This would give you the total number of duplicates…

select count(*) from someTable;
select count(distinct Email) from someTable;

In fact, I don’t know if this will work, but you could try doing it all in one query:

select (count(*)-(count(distinct Email))) from someTable

Like I said, untested, but let me know if it works for you.