How much space a Date , time , TimeStamp column occupy?

Question

Hi
what is size of a Date , Time and TimeStamp type ?
i mean how much bytes they require ?
Thanks

Answer 1

Apologies if this posts more than once. I got server errors.
Laurent:
Sysdate and systimestamp are actually different types than a date or timestamp column.
SQL> CREATE TABLE dt (dt DATE, ts TIMESTAMP);
Table created.
SQL> INSERT INTO dt VALUES(sysdate, systimestamp);
1 row created.
SQL> COMMIT;
Commit complete.
DUMP(DT)
Typ=12 Len=7: 120,106,6,2,17,43,10
SQL> SELECT DUMP(ts) FROM dt;
DUMP(TS)
Typ=180 Len=11: 120,106,6,2,17,43,10,28,185,249,48
SQL> SELECT DUMP(sysdate) from dual;
DUMP(SYSDATE)
Typ=13 Len=8: 7,214,6,2,16,50,17,0
SQL> SELECT DUMP(systimestamp) from dual;
DUMP(SYSTIMESTAMP)
Typ=188 Len=20: 7,214,6,2,20,50,30,0,48,111,78,168,252,0,5,0,0,0,0,0I seem to recall reading somewhere that sysdate is actually a representation of the C struct_t time structure, while a date column is Oracle's internal format. It looks like something similar is going on with systimestamp, and with the date and timestamp casts you are doing.
The inserts into the table above were done minutes before the selects, but definitely within the same hour. The byte values have no correlation, between the date field and sysdate, nor between the timestamp field and systimestamp, while the the date and timestamp fields are identical to the second. Similarly, the sysdate and systimestamp dumps are identical to the second.
The vsize function reports the physical storage required for the expression passed. My guess would be that it is implicitly casting sysdate and systimestamp to the equivalent internal representation before calculating the size.
John