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POPostgresql select people you may know orderded by number of mutual friends
 

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    <p>I'm building a social network, and I want my members to be able to easily find new friends. Just like in Facebook, I want to suggest them some people they may know by the number of mutual friends they have.</p> <p>My PostgreSQL database structure for friendships is as following:</p> <pre><code>&gt; PROFILES_FRIENDSHIPS &gt; ---------------------- &gt; - fri_profile_from // int, Person who sent the friendship request &gt; - fri_profile_to // int, Person who received the friendship request &gt; - fri_accepted // tinyint, has the person accepted the friendship request? </code></pre> <p>This is the query I figured out in PostgreSQL for finding the number of mutual friends between 2 profiles (profile with ID 24, and profile with ID 26):</p> <pre><code>SELECT COUNT(*) FROM profiles AS p INNER JOIN ( SELECT ( CASE WHEN ( 26 = f.fri_profile_from ) THEN f.fri_profile_to ELSE f.fri_profile_from END) AS fri_profile_from FROM profiles_friendships AS f WHERE 1 = 1 AND (f.fri_profile_to = 26 OR f.fri_profile_from = 26) AND fri_accepted = 1) AS f1 ON (f1.fri_profile_from = p.pro_id) INNER JOIN ( SELECT ( CASE WHEN ( 24 = f.fri_profile_from ) THEN f.fri_profile_to ELSE f.fri_profile_from END) AS fri_profile_from FROM profiles_friendships AS f WHERE 1 = 1 AND (f.fri_profile_to = 24 OR f.fri_profile_from = 24) AND fri_accepted = 1) AS f2 ON (f2.fri_profile_from = p.pro_id) </code></pre> <p>Now I have been trying to convert this query to make it find the profiles with the most mutual friends of me, but who are not friends with me. But without success... I also researched a lot of examples on this website, but most them are working with double records in the friendships table. Like if 24 is friends with 26, there are 2 records: (24, 26) and (26, 24). That makes them easier to join and to find mutual friends, but that's not how I want to build my database.</p> <p>If someone could help me to get started on this query, I would be very grateful.</p>
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