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
    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 tab3.b3
        Function plus (children 1)
         ExpressionList (children 2)
          Identifier a2
          Identifier b2