Question

I want to select rows that have a distinct email, see the example table below:

+----+---------+-------------------+-------------+
| id | title   | email             | commentname |
+----+---------+-------------------+-------------+
|  3 | test    | [e-mail]   | rob         |
|  4 | i agree | [e-mail]   | rob         |
|  5 | its ok  | [e-mail]   | rob         |
|  6 | hey     | [e-mail]   | rob         |
|  7 | nice!   | [e-mail] | simon       |
|  8 | yeah    | [e-mail]  | john        |
+----+---------+-------------------+-------------+

The desired result would be:

+----+-------+-------------------+-------------+
| id | title | email             | commentname |
+----+-------+-------------------+-------------+
|  3 | test  | [e-mail]   | rob         |
|  7 | nice! | [e-mail] | simon       |
|  8 | yeah  | [e-mail]  | john        |
+----+-------+-------------------+-------------+

Where I don’t care which id column value is returned.
What would be the required SQL?

Answer 1

Quick one in TSQL

SELECT a.*
FROM emails a
INNER JOIN 
  (SELECT email,
    MIN(id) as id
  FROM emails 
  GROUP BY email 
) AS b
  ON a.email = b.email 
  AND a.id = b.id;