if (query.getLeft() == null) {
// leaf node
return queryComparison(query);
} else {
int operator = query.getOperator();
WorkflowQuery left = query.getLeft();
WorkflowQuery right = query.getRight();
switch (operator) {
case WorkflowQuery.AND:
return "(" + queryWhere(left) + " AND " + queryWhere(right) + ")";