MySQL: Apply ORDER BY on a field having datatype varchar

Question

I have a db table like:

----------------------------
id  name        cat
============================
1   20.gif      logo
2   21.gif      logo
3   22.gif      logo
4   15.gif      web
5   16.gif      web
6   17.gif      web
7   23.gif      logo
8   18.gif      web
9   19.gif      web

and I want to fetch highest (latest inserted record for each cat) some thing like:

----------------------------
id  name        cat
============================
7   23.gif      logo
9   19.gif      web

for this I queried:

SELECT id, name, cat FROM portfolio GROUP BY cat ORDER BY name DESC

but because name field is an string so I cant apply ORDER BY on name.

any idea..?

Answer 1

SELECT id, name, cat 
FROM portfolio 
GROUP BY cat 
ORDER BY cast(substring(name, 1, INSTR(name, '.') - 1) as signed) DESC    

SQLFiddle example

Answer 2

Yes I found the solution :

select id, name, cat from (select * from portfolio ORDER BY id DESC) AS x GROUP BY cat

I got help from Retrieving the last record in each group

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