public static <T> Expression<T> union(List<SubQueryExpression<T>> union, Path<T> alias,
            boolean unionAll) {
        final Expression<T> rv = union(union, unionAll);
        return ExpressionUtils.as(rv, alias);
    }
UnionUtils provides static utility methods for Union handling

@author tiwe
querydsl-sql/src/main/java/com/querydsl/sql/UnionUtils.java