How best to think about keeping "cool""not cool" for articles or posts in the database?

Well if you only need to consider, it is enough just to add rating field in the table article and increase / decrease its value programmatically.
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The table is only needed when you want to impose a time limit Ah-PI the address, and so it is considered Good practice not to store the IP address as a string and write its numeric value (if you write in php php.net/manual/en/function.ip2long.php).
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Moreover, when outputting the news feed is very useful aggregatirovanie the rating value has to be stored in a separate field in the table articles — that would not be recalculated each time. To update it you can trigger on the side of the DBMS or software.

by ip is not very good because some providers on a bunch of users immediately hang up 1 ip, and the users of the mobile Internet so generally often 1 ip on all
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IMHO you'd better get decent to set a cookie with some unique token, and for her to watch than the ip

In addition to the previous speaker, the sad experience — from cheating to get impossible. You can only minimize it by a set of administrative and technical methods.