SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 4)
    Identifier a2
    Identifier b2
    Identifier a3
    Identifier b3
   TablesInSelectQuery (children 2)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      TableIdentifier tab2
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      TableIdentifier tab3
     TableJoin (children 1)
      Function and (children 1)
       ExpressionList (children 2)
        Function equals (children 1)
         ExpressionList (children 2)
          Identifier a2
          Identifier a3
        Function equals (children 1)
         ExpressionList (children 2)
          Identifier b2
          Identifier b3