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