Title：
Write an SQL query to find all duplicate e-mails in the Person table.
Example :
case:
+----+---------+ | Id | Email | +----+---------+ | 1 | [email protected] | | 2 | [email protected] | | 3 | [email protected] | +----+---------+
return:
+---------+ | Email | +---------+ | [email protected] | +---------+
Note:
All Email is lowercase letters.
Analysis of Title：
None
Test case：
{"headers": {"Person": ["Id", "Email"]}, "rows": {"Person": [[1, "[email protected]"], [2, "[email protected]"], [3, "[email protected]"]]}}
MySQL：
select Email from Person group by Email having count(*)>1;
Analysis of Code：
We need to return(or so-called select) Emali non-repetitive.
The first key is 'all duplicate', so we need to 'group by'.
The second key is 'repeated', so it means the count is greater than 1, so we select count(*>1)