SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function if (alias x) (children 1)
     ExpressionList (children 3)
      Function CAST (children 1)
       ExpressionList (children 2)
        Literal NULL
        Literal \'Nullable(UInt8)\'
      Literal \'2.55\'
      Literal NULL