public void addOrderByColumn(String table, String columnName, SQLObject expr) {
Column column = new Column(table, columnName);
SQLObject parent = expr.getParent();
if (parent instanceof SQLSelectOrderByItem) {
SQLOrderingSpecification type = ((SQLSelectOrderByItem) parent).getType();
column.getAttributes().put("orderBy.type", type);
}
orderByColumns.add(column);
}