Ordering by inches value in MYSQL - mysql

Question

I've searched for the answer to this but can't quite work it out. I think I'm close but need your help please.
I have the following mysql query:
SELECT `size`
FROM `table`
GROUP BY `size`
ORDER BY CONVERT(SUBSTR(size, 1, POSITION('/' IN size) - 1), UNSIGNED INTEGER) ASC,
SUBSTRING_INDEX(size,'/',1)/SUBSTRING_INDEX(size,'/',-1) ASC
Running this gives the following result:
1"
2"
4"
3"
1/2"
3/8"
3/4"
11/4"
11/2"
21/2"
I need the sizes to come out smallest to largest. Any help on this would be massively appreciated. Thank you.
Note, I have also tried removing the " from the sizes in the database and the result was exactly the same.
An example of the dataset:
1 1/2"
1 1/4"
1"
1/2"
1/4"
1/8"
10"
11/2"
11/4"
11/4""
12"
14"
16"
2 1/2"
2"
21/2"
3"
3/4"
3/8"
4"
5"
6"
8"

Answer 1

Lovely data format. I think you are going to have to do the division. The calculation is something like this:
order by (case when size like '%/%'
then (substring_index(size, '/', 1) + 0) / (substring_index(size, '/', 2) + 0)
else size + 0
end)
Even if the " is part of the field, this will still work. The + 0 does "silent" conversion. That is, it converts the string up to the first non-numeric character.
EDIT:
If you could have spaces with whole numbers first, you would do:
order by (case when size like '% %/%'
then (substring_index(size, 1, ' ') + 0) +
((substring_index(substring_index(size, ' ', 2), '/', 1) + 0) /
(substring_index(size, '/', -1) + 0)
)
when size like '%/%'
then (substring_index(size, '/', 1) + 0) / (substring_index(size, '/', 2) + 0)
else size + 0
end)

Answer 2

You query almost work. However in first part of the order by you should substract the position from the string length.
SELECT `size`
FROM `size`
GROUP BY `size`
ORDER BY CONVERT(SUBSTR(size, 1, LENGTH(size) - POSITION('/' IN size) - 1), UNSIGNED INTEGER) ASC,
SUBSTRING_INDEX(size,'/',1)/SUBSTRING_INDEX(size,'/',-1) ASC
http://sqlfiddle.com/#!2/cd0658/6