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 (alias third)
     TableJoin (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Function plus (children 1)
         ExpressionList (children 2)
          Identifier third.a3
          Identifier tab3.b3
        Function plus (children 1)
         ExpressionList (children 2)
          Identifier tab2.a2
          Identifier second_.b2
