15.00 - Breadth First Reporting - Teradata Database

Teradata Database SQL Data Definition Language Detailed Topics

Teradata Database
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Breadth First Reporting

You can simulate a BFS result by ordering the final result by the depth of the recursion. For example, consider the following view definition.

    CREATE RECURSIVE VIEW reachable_from (destin, cost, depth) AS (
      SELECT root.destin, root.cost, 0 AS depth
      FROM flights AS root
      WHERE root.source = 'paris'            
      SELECT result.destin, seed.cost+result.cost, seed.depth+1 AS depth
      FROM reachable_from AS seed, flights AS result    
      WHERE seed.destin = result.source
      AND   depth <= 20);

By ordering the query result on the depth variable, the following SELECT request provides a breadth first report on this view.

    SELECT * 
    FROM reachable_from 
    ORDER BY depth;