以升序获取表中的字母数字值

Question

I have a table Food which contains column Quantity(it contains values- 10 kg,32 kg,5 kg). I want to fetch Quantity values in acsending order .

Now I have query:

select Quantity from Food

output=>

10 kg

32 kg

5 kg

But expected result is :

5 kg

10 kg

32 kg

How can I sort this alphanumeric value in SQL?

Answer 1

Try:

SELECT Quantity from Food ORDER BY CAST(Quantity as UNSIGNED) DESC;

This isn't ideal, you should store the quantity as an integer field and the unit as an enum.

Answer 2

If the unit is only kg then you can try like below. See a demo fiddle here http://sqlfiddle.com/#!9/e644f/6

select Quantity from Food
order by replace(Quantity,'kg','') * 1;

Answer 3

Depending on the actual data you can grab the numeric part from the front of the value and than order by it:

SELECT Quantity 
  FROM Food 
 ORDER BY CAST(LEFT(Quantity,INSTR(Quantity,' ')-1) AS DECIMAL) DESC;

However as @Martin indicates MySQL appear to do that much for you. This is more explicit and there is, perhaps, value in that.