Simple mysql query. Help

[shortysbest]

I have a database called "postvoting", It's basically to store when somebody votes on a particular posts. I store the post_id that the user votes on, the users id that voted on it, and the date.

What I want to do is find the most popular posts in a given time.

 

So if 4 people voted on the post with the id of 1, and 2 people voted on the post with the id of 2, I want to count the number of rows with post_id='1'

 

A non working example what I want would look something like:

$count_votes = mysql_query("SELECT * FROM postvoting WHILE post_id=post_id");

print mysql_num_rows($count_votes);

result: 4

 

or

$count_votes = mysql_query("SELECT * FROM postvoting GROUP BY post_id");

print mysql_num_rows($count_votes);

result: 4

 

(counting the number of results in a group)

 

Hope this isn't too confusing. (I've confused myself with this).

 

[fortnox007]

here you go: http://www.w3schools.com/sql/sql_groupby.asp