SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 2)
    Identifier a2
    Identifier b2
   TablesInSelectQuery (children 2)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier tab2 (alias second_)
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier tab3
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Function plus (children 1)
         ExpressionList (children 2)
          Identifier a3
          Identifier b3
        Function plus (children 1)
         ExpressionList (children 2)
          Identifier a2
          Identifier second_.b2