如何获取相关的mysql php记录？

I have mysql table 'files'. which contains following order. 1. id 2.filename 3.keywords

When displaying one file i want to show the related files from same database table order by most matched keywords.

should it be like

 $keywords = $db->getkeywords('5');

 //getting related files

 $sql = "select * from 'file's where 'keywords' like '$keywords'";

????

Use something like this:

$keywords = join(',' $db->getkeywords('5')); 
$sql = "SELECT * FROM files WHERE keywords IN ($keywords)";