Explain EXPLAIN PIPELINE (children 1)
 InsertQuery   (children 2)
  Identifier t_mt
  SelectWithUnionQuery (children 1)
   ExpressionList (children 1)
    SelectQuery (children 2)
     ExpressionList (children 1)
      Asterisk
     TablesInSelectQuery (children 1)
      TablesInSelectQueryElement (children 1)
       TableExpression (children 1)
        TableIdentifier system.one
