Is there a way in SQL (MySQL) to do a “round robin” ORDER BY on a particular field?

Question

Is there a way in SQL (MySQL) to do a \"round robin\" ORDER BY on a particular field?

As an example, I would like to take a table such as this one:

Answer 1

You can use MySQL variables to do this.

SELECT grp, name, @row:=@row+1 from table, (SELECT @row:=0) r ORDER BY (@row % 3);

+------+------+--------------+
| grp  | name | @row:=@row+1 |
+------+------+--------------+
|    1 | A    |            1 |
|    2 | D    |            4 |
|    3 | G    |            7 |
|    1 | B    |            2 |
|    2 | E    |            5 |
|    3 | H    |            8 |
|    1 | C    |            3 |
|    2 | F    |            6 |
|    3 | I    |            9 |
+------+------+--------------+

Answer 2

I'd try something like:

SET @counter = 0;
SELECT (@counter:=@counter+1)%3 as rr, grp, name FROM table ORDER by rr, grp 

Answer 3

What you can do is create a temporary column in which you create sets to give you something like this:

+-------+------+-----+
| group | name | tmp |
+-------+------+-----+
|     1 | A    |   1 |
|     1 | B    |   2 |
|     1 | C    |   3 |
|     2 | D    |   1 |
|     2 | E    |   2 |
|     2 | F    |   3 |
|     3 | G    |   1 |
|     3 | H    |   2 |
|     3 | I    |   3 |
+-------+------+-----+

To learn how to create the sets, have a look at this question/answer.

Then its a simple

ORDER BY tmp, group, name