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POMySQL Query to find friends and number of mutual friends
 

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    <p>I have looked through the questions but I cant find anything that does exactly what I need and I can't figure out how to do it myself.</p> <p>I have 2 tables, a user table and a friend link table. The user table is a table of all my users:</p> <pre><code> +---------+------------+---------+---------------+ | user_id | first_name | surname | email | +---------+------------+---------+---------------+ 1 joe bloggs joe@test.com 2 bill bloggs bill@test.com 3 john bloggs john@test.com 4 karl bloggs karl@test.com </code></pre> <p>My friend links table then shows all relationships between the users, for example:</p> <pre><code> +--------=+---------+-----------+--------+ | link_id | user_id | friend_id | status | +---------+---------+-----------+--------+ 1 1 3 a 2 3 1 a 3 4 3 a 4 3 4 a 5 2 3 a 6 3 2 a </code></pre> <p>As a note the a in the status column means approved, there could also be r(request) and d(declined).</p> <p>What I want to do is have a query where if a user does a search it will bring back a list of users that they are currently not already friends with and how many mutual friends each user has with them.</p> <p>I have managed to get a query for all users that are currently not friends with them. So if the user doing the search had the user id of 1:</p> <pre><code>SELECT u.user_id,u.first_name,u.surname FROM users u LEFT JOIN friend_links fl ON u.user_id = fl.user_id AND 1 IN (fl.friend_id) WHERE fl.friend_id IS NULL AND u.user_id != 1 AND surname LIKE 'bloggs' </code></pre> <p>How then do I have a count of the number of mutual friends for each returned user?</p> <p><strong>EDIT:</strong></p> <p>Just as an edit as I don't think I am being particularly clear with my question.</p> <p>The query that I currently have above will produce the following set of results:</p> <pre><code> +---------+------------+---------+ | user_id | first_name | surname | +---------+------------+---------+ 2 bill bloggs 4 karl bloggs </code></pre> <p>Those are the users matching the surname bloggs that are not currently friends with joe bloggs (user id 1).</p> <p>Then I want to have how many mutual friends each of these users has with the user doing the search so the returned results would look like:</p> <pre><code> +---------+------------+---------+--------+ | user_id | first_name | surname | mutual | +---------+------------+---------+--------+ 2 bill bloggs 1 4 karl bloggs 1 </code></pre> <p>Each of these returned users has 1 mutual friend as joe bloggs (user id 1) is friends with john bloggs and john bloggs is friends with both returned users.</p> <p>I hope this is a bit more clear.</p> <p>Thanks.</p>
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