
```
select *
from (
select 'table' as table, toInt64(10) as rows, toInt64(101) as elements
union all
select 'another table' as table, toInt64(0) as rows, toInt64(0) as elements
)
where rows - elements <> 0

DB::Exception: Block structure mismatch in Pipe::unitePipes stream: different number of columns:
table String String(size = 0), rows Int64 Int64(size = 0), elements Int64 Int64(size = 0)
table String String(size = 0), rows Int64 Int64(size = 0), elements Int64 Int64(size = 0), dummy UInt8 UInt8(size = 0) (version 21.5.3.1 (official build))
```
{
    std::sort(index.begin(), index.end(), [&key_names_pos_map](const Node * lhs, const Node * rhs)
    {
        return key_names_pos_map.find(lhs->result_name)->second < key_names_pos_map.find(rhs->result_name)->second;
    });
}
void ActionsDAG::addAggregatesViaProjection(const Block & aggregates)
{
    for (const auto & aggregate : aggregates)
        index.push_back(&addInput(aggregate));
}
void ActionsDAG::addAliases(const NamesWithAliases & aliases)
{
    std::unordered_map<std::string_view, size_t> names_map;
    for (size_t i = 0; i < index.size(); ++i)
        names_map[index[i]->result_name] = i;
    NodeRawConstPtrs required_nodes;
    required_nodes.reserve(aliases.size());
    for (const auto & item : aliases)
    {
        auto it = names_map.find(item.first);
        if (it == names_map.end())
            throw Exception(ErrorCodes::UNKNOWN_IDENTIFIER,
                            "Unknown column: {}, there are only columns {}", item.first, dumpNames());
        required_nodes.push_back(index[it->second]);