AS OF TIMESTAMP

SELECT * FROM employees

AS OF TIMESTAMP

TO_TIMESTAMP('2004-04-04 09:30:00', 'YYYY-MM-DD HH:MI:SS')

WHERE last_name = 'Chung';

decr encr

 FUNCTION decr (var1 varchar) RETURN CHAR IS

 LEN Number(2) ;

 i  Number(2) ;

 CONV_LET  Varchar2(1) ;

 CONV_STR  Varchar2(30) ;

 incr number;

Begin

 LEN:=To_number(Length(Var1));

 incr:=20;

 For i in 1..Len Loop

   conv_let:=chr(Ascii(Substr(Var1, i,1)) - (incr+i+len));

   conv_str := conv_str||conv_let;

 End Loop ;

 Return Conv_str;

END;

/

FUNCTION encr (var1 varchar) RETURN CHAR IS

 LEN Number(2) ;

 i  Number(2) ;

 CONV_LET  Varchar2(1) ;

 CONV_STR  Varchar2(30) ;

 incr number;

Begin

 LEN:=To_number(Length(Var1));

   incr:=20;

 For i in 1..Len Loop

   conv_let:=chr(Ascii(Substr(upper(Var1), i,1)) + (incr+i+len));

   conv_str := conv_str||conv_let;

 End Loop ;

 Return Conv_str;

END;