SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 4)
   ExpressionList (children 1)
    Function max (children 1)
     ExpressionList (children 1)
      Identifier a
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier tt_m
   ExpressionList (children 1)
    Identifier b
   ExpressionList (children 1)
    OrderByElement (children 1)
     Identifier b
