@Override
    public T fetchOne() throws NonUniqueResultException {
        if (getMetadata().getModifiers().getLimit() == null
            && !queryMixin.getMetadata().getProjection().toString().contains("count(")) {
            limit(2);
        }
        CloseableIterator<T> iterator = iterate();
        return uniqueResult(iterator);
    }
Creates an union expression for the given subqueries

@param <RT>
@param alias alias for union
@param sq subqueries
@return the current object
querydsl-sql/src/main/java/com/querydsl/sql/ProjectableSQLQuery.java