SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Function CAST (alias x) (children 1)
     ExpressionList (children 2)
      Identifier a
      Literal \'Int32\'
    Function toTypeName (children 1)
     ExpressionList (children 1)
      Identifier x
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Function materialize (alias a) (children 1)
            ExpressionList (children 1)
             Function CAST (children 1)
              ExpressionList (children 2)
               Literal NULL
               Literal \'Nullable(UInt8)\'