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plurals

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Id
1978005
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0
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2009-12-30T01:52:49.257
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2009-12-30T01:52:49.257
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text
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The simple approach would be to do some kind of simple nested clause. So say you have a table with posts and the posters id, and a friends table, the first layer would be <pre><code>SELECT post FROM posts JOIN friends on post.userid = friends.friend_id WHERE friend.id = 1 (user ID) </code></pre> then to get a friends of friends <pre><code>SELECT post FROM posts JOIN (SELECT DISTINCT friends_2.friend_id FROM friends AS friends_1 JOIN friends as friends_2 on friends_1.friend_id = friends_2.id where friends_1.id = 1) AS friends wHERE post.userid = friends.friend_id AND mainid = 1 (user ID) </code></pre> You can repeat this nesting each time you want to add another layer of friend abstraction. The problem with this approach is that it would take a very long time to execute. For every time you add a layer of friend abstraction you are increasing the complexity by a power of n (where n is the number of rows in your table). It is more likely that they are saving the viewable friends in a table somewhere, so lets make a new tabled called friends_web <pre><code>user_id, friend_id, level </code></pre> when a user friends someone, it adds that new friend into friends_web at a level of 0(since that friend is no people away) then adds that friends friends at a level of 1 (since its 1 friend away). In order to keep the table integrity you would also want to add the inverted record. To clarify if A adds B as a friend and C is a friend of B, the following two records would get added to our new table <pre><code>A, C, 1 C, A, 1 </code></pre> since now A can see C and C can see A. now when we want a query we just do <pre><code> SELECT post FROM posts JOIN friends_web ON post.user_id = friends_web.friend_id WHERE friends_web.user_id = user_id AND friends_web.level < 2 (or however deep you want to look) </code></pre> by doing that you minimized your query complexity when doing post lookups while being able to look more then 1 layer deep into a friend web. Sorry for the long winded response.
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1. This table or related slice is empty.
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1. POFriend of a friend in PHP/MySQL?
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1. PTAnswer
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1. This table or related slice is empty.
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1. USDidius
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1. VO
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