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POAdvanced graph SQL question
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copied!<p>I have a directed graph described by <code>A -> B</code> meaning that there exists a connection, always weight 1, FROM A TO B. The problem I want to solve (This is not an academic project) is how can I tell how many common connections there are between two nodes. </p> <p>To say that in terms of A and B.<br> There are 2 things that need to get done,<br> * To look at all of my, B, links coming in (All A's to some B)<br> * Count how many common A's out of all My, Original B, A's. </p> <p>I do not know if that makes sense but I'll show you how far I have come.<br> * First point. </p> <pre><code>SELECT A FROM graph WHERE B='myid'; </code></pre> <p>As most can tell, part 1 is a very simple question. Part 2 is where things get tricky.<br> I have been able to get all the A's with at least 1 connection or more similar. </p> <p>Second point. </p> <pre><code>SELECT G.A, count( G2.A ) AS common FROM graph AS G2 JOIN ( SELECT A, B FROM graph WHERE B = 'myid' ) AS G ON G.A = G2.B </code></pre> <p>So the second point is close because it will return all common links, <strong>but</strong> it will not return all links which have no common links. Is there a way to get that too? </p> <hr> <p>There is still confusion: Ill try to draw a picture... with words.<br> Here is the table. </p> <pre><code>A, B ----- 2, 1 3, 1 2, 3 </code></pre> <p>If I wanted to see how many common links from all incoming links into NODE 1 I <strong>should</strong> see </p> <pre><code>A, count --------- 2, 1 // This is for 2's connection to 3. 3, 0 </code></pre> <p>With the current SQL statement I have I see this.</p> <pre><code>A, count --------- 2, 1 // This is for 2's connection to 3. </code></pre>

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