SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function ifNull (alias res) (children 1)
     ExpressionList (children 2)
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'x\'
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'y\'
    Function toTypeName (children 1)
     ExpressionList (children 1)
      Identifier res
