ref #9436
Currently EPHEMERAL column requires an explicit default value provided on CREATE TABLE - we can allow implicit default there

{
                auto projection = ProjectionDescription::getProjectionFromAST(projection_ast, properties.columns, getContext());
                properties.projections.add(std::move(projection));
            }
        properties.constraints = getConstraintsDescription(create.columns_list->constraints);
    }
    else if (!create.as_table.empty())
    {
        String as_database_name = getContext()->resolveDatabase(create.as_database);
        StoragePtr as_storage = DatabaseCatalog::instance().getTable({as_database_name, create.as_table}, getContext());
        
        as_storage_lock = as_storage->lockForShare(getContext()->getCurrentQueryId(), getContext()->getSettingsRef().lock_acquire_timeout);
        auto as_storage_metadata = as_storage->getInMemoryMetadataPtr();
        properties.columns = as_storage_metadata->getColumns();
        
        
        if (create.storage && endsWith(create.storage->engine->name, "MergeTree"))
        {
            properties.indices = as_storage_metadata->getSecondaryIndices();
            properties.projections = as_storage_metadata->getProjections().clone();
        }
        else
        {
            
            properties.columns.resetColumnTTLs();
        }
        properties.constraints = as_storage_metadata->getConstraints();
    }
    else if (create.select)
    {