How to add “weights” to a MySQL table and select random values according to these?

Question

I want to create a table, with each row containing some sort of weight. Then I want to select random values with the probability equal to (weight of that row)/(weight of all

Answer 1

I came looking for the answer to the same question - I decided to come up with this:

id      weight
1       5
2       1

SELECT * FROM table ORDER BY RAND()/weight

it's not exact - but it is using random so i might not expect exact. I ran it 70 times to get number 2 10 times. I would have expect 1/6th but i got 1/7th. I'd say that's pretty close. I'd have to run a script to do it a few thousand times to get a really good idea if it's working.