@Override
    public WithBuilder<Q> with(Path<?> alias, Path<?>... columns) {
        Expression<?> columnsCombined = ExpressionUtils.list(Object.class, columns);
        Expression<?> aliasCombined = Expressions.operation(alias.getType(), SQLOps.WITH_COLUMNS, alias, columnsCombined);
        return new WithBuilder<Q>(queryMixin, aliasCombined);
    }
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