How to select one row randomly taking into account a weight?

Question

I have a table which looks like that:

id: primary key
content: varchar
weight: int

What I want to do is randomly select one row from this t

Answer 1

This works in MSSQL and I am sure that it should be possible to change couple of keywords to make it work in MySQL as well (maybe even nicer):

SELECT      TOP 1 t.*
FROM        @Table t
INNER JOIN (SELECT      t.id, sum(tt.weight) AS cum_weight
            FROM        @Table t
            INNER JOIN  @Table tt ON  tt.id <= t.id
            GROUP BY    t.id) tc
        ON  tc.id = t.id,
           (SELECT  SUM(weight) AS total_weight FROM @Table) tt,
           (SELECT  RAND() AS rnd) r
WHERE       r.rnd * tt.total_weight <= tc.cum_weight
ORDER BY    t.id ASC

The idea is to have a cumulative weight for each row (subselect-1), then find the position of the spanned RAND() in this cumulative range.