SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function concat (children 1)
     ExpressionList (children 1)
      Function materialize (children 1)
       ExpressionList (children 1)
        Function CAST (children 1)
         ExpressionList (children 2)
          Literal NULL
          Literal \'Nullable(UInt64)\'