Length vs vsize?use of vsize in practical scenario?

Question

what is the actual difference between length and vsize function.?
on what condition vsize function should be used ?
how does vsize calculates for date and number datatype?
i came across these things
can you please tell me why this type of result is coming.
SQL> select vsize(1234567890123) from dual;
VSIZE(1234567890123)
8
SQL> select vsize(12345678901234) from dual;
VSIZE(12345678901234)
8
SQL> select vsize(sysdate) from dual;
VSIZE(SYSDATE)
7
why the size of sysdate is 7.....and the size of these
two different number with different length is same.
thanks

Answer 1

Look at the DUMP function to see how a value is stored internally, for example:
SQL> create table test_sizes (num number, dt date, str varchar2(20));
Table created.
SQL> insert into test_sizes values (1, sysdate, 'One');
1 row created.
SQL> insert into test_sizes values (100, DATE '2008-01-01', 'One hundred');
1 row created.
SQL> col dump(num) format a30
SQL> col dump(dt) format a40
SQL> col dump(str) format a60
SQL> SELECT num, vsize(num), dump(num) from test_sizes;
       NUM VSIZE(NUM) DUMP(NUM)
         1          2 Typ=2 Len=2: 193,2
       100          2 Typ=2 Len=2: 194,2
2 rows selected.
SQL> SELECT dt, vsize(dt), dump(dt) from test_sizes;
DT         VSIZE(DT) DUMP(DT)
08-MAY-08          7 Typ=12 Len=7: 120,108,5,8,8,38,28
01-JAN-08          7 Typ=12 Len=7: 120,108,1,1,1,1,1
2 rows selected.
SQL> SELECT str, vsize(str), dump(str) from test_sizes;
STR                  VSIZE(STR) DUMP(STR)
One                           3 Typ=1 Len=3: 79,110,101
One hundred                  11 Typ=1 Len=11: 79,110,101,32,104,117,110,100,114,101,100
2 rows selected.I was a little puzzled by vsize(sysdate) being 7 as well. I suppose it must be converting it from an inline date (type 13, 8 bytes) into the stored-date format (type 12, 7 bytes).
Message was edited by:
William Robertson