
```
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))
```
{
    for (const auto & input : inputs_)
    {
        if (input.column && isColumnConst(*input.column))
        {
            addInput(input);
            
            
            
            
            
            
            index.push_back(&addColumn(input));
        }
        else
            index.push_back(&addInput(input.name, input.type));
    }
}
ActionsDAG::Node & ActionsDAG::addNode(Node node)
{
    auto & res = nodes.emplace_back(std::move(node));
    if (res.type == ActionType::INPUT)
        inputs.emplace_back(&res);
    return res;
}
const ActionsDAG::Node & ActionsDAG::addInput(std::string name, DataTypePtr type)