Question

I’m trying to come up with a nice elegant solution for a voting system like SO’s. If there’s a way to do it with elegance using triggers I couldn’t figure it out so I’m trying with stored procedures. This is what I’ve come up with, It’s not pretty so I’m asking for ideas. I’ll probably even have one query rather than the query+stored procedure. But I’d really like to know a clean way to update a user’s points and insert/update votes. Points are in a separate table to be updated by procedure.

Upvote

INSERT INTO votes
ON DUPLICATE KEY
UPDATE votes
SET v.weight = v.weight + 1
WHERE v.weight = 0 OR v.weight = -1
AND v.userid = {$uid}
AND v.itemid = {$itemid}
//call procedure to +1 user points

Downvote

INSERT INTO votes
ON DUPLICATE KEY
UPDATE votes
SET v.weight = v.weight - 1
WHERE v.weight = 1 OR v.weight = 0
AND v.userid = {$uid}
AND v.itemid = {$itemid}
//call procedure to -1

Flipdown (when user changes vote from up to down)

INSERT INTO votes
ON DUPLICATE KEY
UPDATE votes
SET v.weight = -1
WHERE v.weight = 1
AND v.userid = {$uid}
AND v.itemid = {$itemid}
//call procedure to -2

Flipup

INSERT INTO votes
ON DUPLICATE KEY
UPDATE votes
SET v.weight = 0
WHERE v.weight = -1
AND v.userid = {$uid}
AND v.itemid = {$itemid}
//call procedure to +2

Answer 1

I assume that votes table has 3 columns (post_id, user_id, weight). You can use the following query:

insert into votes(post_id, user_id, weight) 
values(post_id_in, user_id_in, weight_in)
on duplicate key update
set
  weight = weight_in;

Use should have unique index on(post_id, user_id).

If you denormalize data and table posts has column for total votes that you need to recalculate it.