SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function materialize (children 1)
     ExpressionList (children 1)
      Literal \'Hello\'
   Function toNullable (children 1)
    ExpressionList (children 1)
     Function materialize (children 1)
      ExpressionList (children 1)
       Literal UInt64_0
