SelectQuery left = (SelectQuery)l;
SelectQuery right = (SelectQuery)r;
if (left.isComplex() || right.isComplex())
return;
left = left.clone();
right = right.clone();
filterOn(left, right);
mergeSelectClause(left, right);
left.addLeftJoin(right);
List<SqlExpr> filters = new ArrayList<SqlExpr>();
if (node.getCondition() != null) {