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databaseSQLQuery.cpp

Shows how retrieve geometries (polygons) using an SQL query.

    /************************************************************************************
    TerraLib - a library for developing GIS applications.
    Copyright � 2001-2004 INPE and Tecgraf/PUC-Rio.

    This code is part of the TerraLib library.
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    You should have received a copy of the GNU Lesser General Public
    License along with this library.

    The authors reassure the license terms regarding the warranties.
    They specifically disclaim any warranties, including, but not limited to,
    the implied warranties of merchantability and fitness for a particular purpose.
    The library provided hereunder is on an "as is" basis, and the authors have no
    obligation to provide maintenance, support, updates, enhancements, or modifications.
    In no event shall INPE and Tecgraf / PUC-Rio be held liable to any party for direct,
    indirect, special, incidental, or consequential damages arising out of the use
    of this library and its documentation.
    *************************************************************************************/

    /*
        This file shows an example of how retrieve geometries (polygons) using an SQL query

               Author: Lubia Vinhas
    */

    #include "../../src/terralib/drivers/MySQL/TeMySQL.h"

    int main()
    {
               // Datatabase server parameters
               string host = "localhost";
               string dbname = "DB320RC1";
               string user = "root";
               string password = "vinhas";

               // Open a connection to a MySQL database
               TeDatabase* db = new TeMySQL();
               if (!db->connect(host, user, password, dbname))
               {
                          cout << "Error: " << db->errorMessage() << endl << endl;
                          cout << "Press Enter\n";
                          getchar();
                          return 1;
               }
               cout << "Connection successful to the database \"" << dbname << "\" on MySQL server \"" << host << "\" !";
               cout << endl << endl;

               // Load a layer by its name
               TeLayer *layer = new TeLayer("Distritos");
               if (!db->loadLayer(layer))
               {
                          cout << "Error: " << db->errorMessage() << endl << endl;
                          db->close();
                          cout << "Press Enter\n";
                          getchar();
                          return 1;
               }

               // Retrieve the information about the polygons representation
               TeRepresentation* rep = layer->getRepresentation(TePOLYGONS);
               if (!rep)
               {
                          cout << "Layer has no polygons representation!" << endl;
                          db->close();
                          cout << "Press Enter\n";
                          getchar();
                          return 1;
               }

               string geomTableName = rep->tableName_;

               // Build the SQL to get the polygons that are inside a given box
               TeBox bb(320100,7390100,337900,7599000);
        string q;
        q = "SELECT * FROM " + geomTableName + " WHERE ";
               q +=  db->getSQLBoxWhere (bb, TePOLYGONS, geomTableName);

        // Get a portal to the database
        TeDatabasePortal *portal = db->getPortal();
        if (!portal)
        {
                          cout << "Fail to get a database portal!\n\n";
                          cout << "Press Enter\n";
                          db->close();
                          getchar();
                          return 1;
        }

        // Submit the query and go to the first position of the portal
        if (!portal->query(q) || !portal->fetchRow())
        {
                          cout << "Fail to submit the query or no records returned\n";
                          delete portal;
                          db->close();
                          cout << "Press Enter\n";
                          getchar();
                          return 1;
       }

        // Process the polygons found
        TePolygonSet ps;
        bool flag = true;
        do
        {
            TePolygon poly;
            flag = portal->fetchGeometry(poly);
            ps.add(poly);
        }
        while (flag);   // while there is a record to be read

        delete portal;

               // Show the result
               unsigned int i, j;

               cout << "Number of polygons found: " << ps.size() << endl;
               for (i=0; i < ps.size(); ++i)
        {
                          TePolygon pol = ps[i];
                          cout << "Geometry id: " << pol[0].geomId() << ", object id: " << pol.objectId() << endl;
                          for (j = 1; j < pol.size(); ++j)
                                      cout << "\t Child id: " << pol[j].geomId() << endl;
               }

               db->close();
               cout << endl << "Press Enter\n";
               cout.flush();
               getchar();
               return 0;
    }

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