Question

I have such a MYSQL table

  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `screen_name` text NOT NULL,
  `user_no` int(20) NOT NULL,
  `avatar` text NOT NULL,
  `name` varchar(50) NOT NULL,
  `location` varchar(50) DEFAULT NULL
  PRIMARY KEY (`id`)

I need to create an SQL query.

• ORDER BY id DESC
• GROUP BY screen_name
• Get “name” and “screen_name” fields
• id between $idmin and $idmax

I will compare the performance of nested query and JOIN query seperately.
Can you propose query words?
Thank you

Edit: For nested query I tried this:

SELECT `name`,`screen_name` FROM `mytable` WHERE `id` IN
(SELECT `id` FROM `mytable` WHERE `id` BETWEEN 100 AND 500 ORDER BY `id` DESC)
GROUP BY `screen_name`

I couldn’t write for joined type.

Edit2: Say it I have such rows:

• id=1, screen_name=mike, name=uk
• id=2, screen_name=albert, name=usa
• id=3, screen_name=ash, name=uk
• id=4, screen_name=albert, name=new_zelland

I need to get results like this:
id=4
id=3
id=1

Answer 1

Your query should be in this format:

SELECT MAX(id) AS max_id, user_no, screen_name
FROM table_name
WHERE id BETWEEN $idmin AND $idmax
GROUP BY screen_name
ORDER BY MAX(id) DESC;

SQLFIDDLE DEMO HERE

or with sub-query:

SELECT a.id, a.name, a.screen_name
FROM example a
    INNER JOIN (SELECT screen_name, MAX(id) id
                FROM example
                WHERE id BETWEEN 1 AND 4
                GROUP BY screen_name
               ) b
        ON a.screen_name = b.screen_name
           AND a.id = b.id
ORDER BY a.id DESC;

SQLFIDDLE DEMO HERE