Is there an automatic modification time stamp type for Oracle columns?

Question

Is there a way to create a timestamp column in Oracle that automatically stores a timestamp of when the record has changed ?

Answer 1

Yes, via a trigger:

create or replace
TRIGGER schema.name_of_trigger
BEFORE INSERT OR UPDATE ON schema.name_of_table
FOR EACH ROW
BEGIN
    :new.modified_on := SYSTIMESTAMP;
END;

This assumes your table has a field called modified_on.

As has been noted above, a trigger is an ideal candidate anytime you have multiple different places where the table gets updated. If you only have one function/procedure that can update the table, just do it there, and skip the trigger.

Answer 2

Tables I've modelled always include:

• CREATED_USER, VARCHAR2
• CREATED_DATE, DATE
• UPDATED_USER, VARCHAR2
• UPDATED_DATE, DATE

...columns. Why implement a trigger when you can set the value at the same time as the INSERT/UPDATE?

INSERT INTO TABLE (...CREATED_DATE, UPDATED_DATE) VALUES (...,SYSDATE, SYSDATE);

UPDATE TABLE
   SET ...,
       UPDATED_DATE = SYSDATE

Answer 3

For oracle I usually use a trigger to update the timestamp field

CREATE OR REPLACE TRIGGER update_timestamp 
  BEFORE INSERT OR UPDATE ON some_table
  FOR EACH ROW
BEGIN
  :NEW.TS := systimestamp;
END;

Oracle does not seem to have a built-in attribute for updating the timestamp field to the current timestamp (unlike other DBs like MySQL).

Answer 4

Pretty sure you have to do this with a trigger in Oracle:

create or replace TRIGGER parkedorder_tbiur
   BEFORE INSERT OR UPDATE
   ON parkedorder
   REFERENCING OLD AS old_row NEW AS new_row
   FOR EACH ROW
BEGIN
   IF INSERTING
   THEN
      IF :new_row.ID IS NULL
      THEN
         SELECT parkedorder_seq.NEXTVAL
           INTO :new_row.ID
           FROM DUAL;
      END IF;
   END IF;

   IF    :new_row.lastupdated <> SYSDATE
      OR :new_row.lastupdated IS NULL
   THEN
      SELECT sysdate
        INTO :new_row.lastupdated
        FROM DUAL;
   END IF;

   SELECT SYS_CONTEXT ( 'USERENV', 'OS_USER' )
     INTO :new_row.lastupdatedby
     FROM DUAL;
END;

Answer 5

Another way to deal with this is by turning on fine-grained audit. The individual rows won't have a timestamp, but you'll have a record of all changes. Overkill in most situations, though -- I usually just use triggers.

If you are OK with nearest .01 seconds, you can use date format and assign sysdate. If you need more detail, use the timestamp.

Answer 6

You can get very close to this by querying ORA_ROWSCN: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/pseudocolumns007.htm#sthref825

This is more accurate if you created the table with the ROWDEPENDENCIES option.

It actually logs the commit time for the record ...

drop table tester 
/

create table tester (col1 number, col2 timestamp)
rowdependencies
/

insert into tester values (1, systimestamp)
/

(approximate five second pause)

commit
/

select t.ora_rowscn,
       SCN_TO_TIMESTAMP(t.ora_rowscn),
       t.col1,
       t.col2
from   tester t
/

ORA_ROWSCN             SCN_TO_TIMESTAMP(T.ORA_ROWSCN) COL1                   COL2
---------------------- ------------------------------ ---------------------- -------------------------
9104916600628          2009-10-26 09.26.38.000000000  1                      2009-10-26 09.26.35.109848000