"where s1.db_id_subgraph = " + Integer.valueOf(id_subgraph).toString() + " and s2.db_id = s1.db_id_edge;";
edgeStatement = connection.prepare(request,false);
while(edgeStatement.step()) {
int db_id_edge = edgeStatement.columnInt(0);
String id_edge = edgeStatement.columnString(1);
Integer db_id_source = (Integer)edgeStatement.columnValue(2);
Integer db_id_target = (Integer)edgeStatement.columnValue(3);
if(db_id_source != null && db_id_target != null) {
StorableVertex source = null, target = null;
for(StorableVertex bufVertex : listVertex) {
if(bufVertex.getStorableId() == db_id_source) {