SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function concat (children 1)
     ExpressionList (children 2)
      Literal \'a\'
      Function __scalarSubqueryResult (children 1)
       ExpressionList (children 1)
        Identifier a
    Function materialize (alias a) (children 1)
     ExpressionList (children 1)
      Literal \'1\'
