SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function max (children 1)
     ExpressionList (children 1)
      Function plus (children 1)
       ExpressionList (children 2)
        Identifier a
        Identifier b
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 2)
           Literal UInt64_1 (alias a)
           Literal UInt64_2 (alias b)
