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 found this nice little algorithm in Quod Libet. You could probably translate it to some procedural SQL.

function WeightedShuffle(list of items with weights):
  max_score ← the sum of every item’s weight
  choice ← random number in the range [0, max_score)
  current ← 0
  for each item (i, weight) in items:  
    current ← current + weight  
    if current ≥ choice or i is the last item:  
      return item i