
```
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))
```
throw Exception(ErrorCodes::LOGICAL_ERROR,
                                    "Cannot find column {} in ActionsDAG result", node->result_name);
                first.inputs.push_back(node);
            }
            else
            {
                inputs_map[node] = it->second.front();
                removed_first_result[it->second.front()] += 1;
                it->second.pop_front();
            }
        }
    }
    
    for (auto & node : second.nodes)
    {
        for (auto & child : node.children)
        {
            if (child->type == ActionType::INPUT)
            {
                auto it = inputs_map.find(child);
                if (it != inputs_map.end())
                    child = it->second;
            }
        }
    }
    for (auto & node : second.index)
    {
        if (node->type == ActionType::INPUT)
        {
            auto it = inputs_map.find(node);