Oracle SQL Experts: SYSTIMESTAMP FAQS

1. What is the difference between SYSTIMESTAMP and SYSDATE?

SYSTIMESTAMP returns the current date and time, including the time zone of the database system. It has more precision (fractions of a second) and includes the time zone offset (e.g., -08:00).
SYSDATE returns the current date and time but does not include time zone information and has less precision (it doesn’t record fractional seconds).

2. Can SYSTIMESTAMP include milliseconds or fractions of a second?

Yes, SYSTIMESTAMP has precision up to 9 digits for fractional seconds (nanosecond precision). For example: 2025-02-28 14:34:56.123456789 -08:00.

3. Does SYSTIMESTAMP always return the database server's time zone?

Yes, SYSTIMESTAMP always returns the system's time zone, not necessarily the session's time zone. It reflects the time zone of the server where the database is hosted.

4. Can I change the time zone used by SYSTIMESTAMP?

No, SYSTIMESTAMP always uses the database server's time zone. If you need to get a timestamp in a different time zone, you should use CURRENT_TIMESTAMP, which respects the session time zone, or you can convert the result to another time zone using FROM_TZ() or AT TIME ZONE.

5. How do I convert SYSTIMESTAMP to a DATE?

You can use the CAST function to convert SYSTIMESTAMP to a DATE if you don’t need the time zone or fractional seconds:

· SELECT CAST(SYSTIMESTAMP AS DATE) FROM dual;

Note that converting to DATE will lose the time zone and fractional seconds precision.

6. What type does SYSTIMESTAMP return?

It returns a TIMESTAMP WITH TIME ZONE data type. This includes the date, time (with fractional seconds), and the time zone offset from UTC.

7. Is SYSTIMESTAMP affected by Daylight Saving Time (DST)?

Yes, the SYSTIMESTAMP value will reflect the system's local time zone, including any adjustments for Daylight Saving Time (DST). For example, during DST, the time zone offset might change, which is reflected in the timestamp returned by SYSTIMESTAMP.

8. How can I use SYSTIMESTAMP in a query?

· SELECT SYSTIMESTAMP FROM dual;

· SELECT SYSTIMESTAMP - INTERVAL '1' HOUR FROM dual;

9. What is the precision of SYSTIMESTAMP?

The precision of SYSTIMESTAMP includes up to nanosecond precision, which is 9 digits in the fractional seconds. It can return a timestamp such as 2025-02-28 14:34:56.123456789 -08:00.

10. Can I store the SYSTIMESTAMP in a column of type DATE or TIMESTAMP?

While you can store a SYSTIMESTAMP in a TIMESTAMP column (which can store both date and time), if you try to store it in a DATE column, you will lose the time zone and fractional seconds.
For example, to store the exact value of SYSTIMESTAMP, you should use a TIMESTAMP WITH TIME ZONE column.

11. How can I use SYSTIMESTAMP in PL/SQL?

In PL/SQL, you can capture the value of SYSTIMESTAMP into a variable and use it in your logic:

· DECLARE

· ts TIMESTAMP WITH TIME ZONE;

· BEGIN

· ts := SYSTIMESTAMP;

· DBMS_OUTPUT.PUT_LINE('Current system timestamp: ' || ts);

· END;

12. What happens if I use SYSTIMESTAMP in a different session or user context?

SYSTIMESTAMP always reflects the time zone and system time of the database server, regardless of the session. It does not depend on the session’s time zone setting, unlike CURRENT_TIMESTAMP, which depends on the session time zone.

13. Can SYSTIMESTAMP be used for auditing?

Yes, SYSTIMESTAMP is often used in auditing, logging, and tracking events in a database to capture the exact date and time an action occurred, including the time zone offset.

14. Is SYSTIMESTAMP the same as CURRENT_TIMESTAMP?

SYSTIMESTAMP returns the current date and time in the system’s time zone.
CURRENT_TIMESTAMP returns the current date and time in the session’s time zone. So, CURRENT_TIMESTAMP can change based on the session’s time zone settings.

15. How can I get the timestamp for a different time zone using SYSTIMESTAMP?

You can convert the timestamp returned by SYSTIMESTAMP to a different time zone using the AT TIME ZONE function:

· SELECT SYSTIMESTAMP AT TIME ZONE 'UTC' FROM dual;

Oracle SQL Experts