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POCommon table expressions, how to avoid infinite recusion when traversing a graph?
 

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  1. POCommon table expressions, how to avoid infinite recusion when traversing a graph?
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    <p>I have a simple weighted graph</p> <pre><code> A 1 / \\ 0.5 / \\0.5 B C </code></pre> <p>Suppose this describes a family and A is the father, B is the son and C is the mother. Let's say B is studying in an university and A has bought an apartment for him. A is living with C in a house which is commonly owned, 50-50.</p> <p>I want to transform the graph into a tree, starting from A: ie. </p> <ul> <li>A owns 50% of the place C is living in</li> <li>A owns 100% of the place B is living in</li> <li>C owns 50% of the place A is living in</li> </ul> <p>The graph and the generated tree could be more elaborate but I hope you get the more general picture.</p> <p>On SQL Server 2005 I have</p> <pre><code>Drop Table #graph; Create Table #graph (FirstVertex VarChar(1) Not Null, SecondVertex VarChar(1) Not Null, Weight float); Insert #graph Values('A','B',1); Insert #graph Values('A','C',0.5); Insert #graph Values('C','A',0.5); </code></pre> <p>and I'm using the following common table expression to traverse the graph, starting from 'A':</p> <pre><code>With GraphRecursion (FirstVertex, SecondVertex, Weight, Level) As ( Select FirstVertex, SecondVertex, Weight, 0 As Level From #graph Where FirstVertex='A' Union all Select a.FirstVertex, a.SecondVertex, a.Weight, b.Level+1 From #graph a Inner Join GraphRecursion b On a.FirstVertex=b.SecondVertex --And b.Level&lt;=1 ) Select * From GraphRecursion; </code></pre> <p>This causes</p> <pre><code>Msg 530, Level 16, State 1, Line 11 The statement terminated. The maximum recursion 100 has been exhausted before statement completion. </code></pre> <p>Limiting the level of recursion by uncommenting the <code>And b.Level&lt;=1</code> gives the expected results, but that's obviously not very useful for any practical use.</p> <p>Is there a way to reference the previous iterations so that in the above example edges (ie. the FirstVertex, SecondVertex pairs) would not be repeated?</p>
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    1. USVille Koskinen
    1. USVille Koskinen
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      1. POCommon table expressions, how to avoid infinite recusion when traversing a graph?
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      1. VTUpMod
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      1. POCommon table expressions, how to avoid infinite recusion when traversing a graph?
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      1. POCommon table expressions, how to avoid infinite recusion when traversing a graph?
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    1. CONot sure if this helps but have you looked into the MAXRECURSION hint: http://msdn.microsoft.com/en-us/library/ms186243.aspx
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      1. POCommon table expressions, how to avoid infinite recusion when traversing a graph?
      1. USKane
 

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