PHP SQL查询：如何选择相同的ID？

My code is:

$vote = DB::SELECT(DB::RAW("SELECT * FROM votes WHERE product_id = product_id; "));

Here[1] is a screenshot of my DB.

I'd like to ask how to select the same Producut Id in the SQL Query?

[1] http://i.stack.imgur.com/z1Jvc.png

If you want to count sum of votes for each product and sort sum of votes from highest to lowest, then your query is:

SELECT 
    product_id, SUM(vote) as `vote_rate` 
FROM 
    votes 
GROUP BY 
    product_id 
ORDER BY 
    `vote_rate` DESC