Adding a interval to a date

Question

I have the number of day and months that I want to add to a date in a number variable, how do I add it or how do I transform a number into an interval of that many months?
I have tried a few things without success:
Works with literals
SQL> select sysdate + interval '5' day from dual;
SYSDATE+IN
11.06.2008
but not with variables
SQL> declare
2 mnd number;
3 begin
4 mnd := 5;
5
6 select sysdate + interval 'mnd' day from dual;
7 end;
8 /
select sysdate + interval 'mnd' day from dual;
ERROR at line 6:
ORA-06550: line 6, column 29:
PL/SQL: ORA-01867: the interval is invalid
ORA-06550: line 6, column 3:
PL/SQL: SQL Statement ignored
SQL> declare
2 mnd number;
3 begin
4 mnd := 5;
5
6 select sysdate + interval mnd day from dual;
7 end;
8 /
select sysdate + interval mnd day from dual;
ERROR at line 6:
ORA-06550: line 6, column 33:
PL/SQL: ORA-00923: FROM keyword not found where expected
ORA-06550: line 6, column 3:
PL/SQL: SQL Statement ignored
Anyone able to give me a pointer?

Answer 1

That's not going to work in PL/SQL, like you have found out.
You can however add the number 5 of course, or use the numtodsinterval function:
SQL> declare
  2    l_number_of_days number := 5;
  3    l_new_date date;
  4  begin
  5    l_new_date := sysdate + interval l_number_of_days day;
  6    dbms_output.put_line(to_char(l_new_date,'dd-mm-yyyy hh24:mi:ss'));
  7  end;
  8  /
  l_new_date := sysdate + interval l_number_of_days day;
FOUT in regel 5:
.ORA-06550: Regel 5, kolom 36:
PLS-00103: Symbool "L_NUMBER_OF_DAYS" aangetroffen terwijl een van de volgende werd verwacht:
. * @ & = - + ; < / > at in is mod remainder not rem
<een exponent (**)> <> or != or ~= >= <= <> and or like like2
like4 likec between || member
<een SQL-string tussen enkele aanhalingstekens> submultiset
Symbool "<een SQL-string tussen enkele aanhalingstekens> werd ingevoegd voor "L_NUMBER_OF_DAYS" om door te gaan.
SQL> declare
  2    l_number_of_days number := 5;
  3    l_new_date date;
  4  begin
  5    l_new_date := sysdate + 5;
  6    l_new_date := sysdate + numtodsinterval(5,'day');
  7    dbms_output.put_line(to_char(l_new_date,'dd-mm-yyyy hh24:mi:ss'));
  8  end;
  9  /
11-06-2008 14:14:09
PL/SQL-procedure is geslaagd.Regards,
Rob.