CURRENT_TIMESTAMP FAQS

 1. What is CURRENT_TIMESTAMP in Oracle

• CURRENT_TIMESTAMP is a built-in function in Oracle.
• It returns the current date and time with the session's time zone information.
• The returned data type is TIMESTAMP WITH TIME ZONE.
• It includes date, time, fractional seconds, and the session's time zone offset from UTC.

2. What data type does CURRENT_TIMESTAMP return?

• CURRENT_TIMESTAMP returns a TIMESTAMP WITH TIME ZONE data type, which includes:
• Date and Time (down to fractional seconds)
• Time Zone offset (e.g., +02:00, -05:00)

 

3. How is CURRENT_TIMESTAMP different from SYSDATE?

SYSDATE 

• Returns the current date and time from the server's system clock, without any time zone information, and in DATE data type (no fractional seconds or time zone).

CURRENT_TIMESTAMP:

•  Returns the current date and time based on the session's time zone, with time zone offset and fractional seconds, and is returned as TIMESTAMP WITH TIME ZONE.

 

4. How does CURRENT_TIMESTAMP handle time zones?

CURRENT_TIMESTAMP 

• uses the session’s time zone to determine the date and time, and it includes the time zone offset in the result.
• If you want to change the time zone for your session, you can use:

ALTER SESSION SET TIME_ZONE = 'America/New_York';

• You can check your session's time zone using:

SELECT sessiontimezone FROM dual;

 

5. Can I use CURRENT_TIMESTAMP to convert between time zones?

• Yes, you can convert a timestamp to a different time zone using the AT TIME ZONE function. 
• For example:

SELECT CURRENT_TIMESTAMP AT TIME ZONE 'UTC' FROM dual;

 

6. How can I get the current timestamp without fractional seconds?

• To get the current timestamp without fractional seconds, you can truncate the value like this:

SELECT CAST(CURRENT_TIMESTAMP AS TIMESTAMP(0)) FROM dual;

 

7. How do I compare CURRENT_TIMESTAMP with other timestamps in a query?

• You can compare CURRENT_TIMESTAMP with other TIMESTAMP columns or expressions. For example:

SELECT * FROM orders

WHERE order_timestamp > CURRENT_TIMESTAMP - INTERVAL '1' DAY;

This would fetch orders placed in the last 24 hours based on the session's current time zone.

 

8. How do I add or subtract time from CURRENT_TIMESTAMP?

• You can use the INTERVAL keyword to add or subtract time. For example:
• Add 5 days to the current timestamp:

SELECT CURRENT_TIMESTAMP + INTERVAL '5' DAY FROM dual;

• Subtract 3 hours from the current timestamp:

SELECT CURRENT_TIMESTAMP - INTERVAL '3' HOUR FROM dual;

 

9. Can CURRENT_TIMESTAMP return different values during query execution?

• Yes, CURRENT_TIMESTAMP is evaluated each time it is called in a query. If the query takes a long time to execute, the timestamp may change during execution. This is because CURRENT_TIMESTAMP reflects the current date and time, which can change in the course of the query’s execution.

 

10. How can I ensure the time zone is consistent in my queries using CURRENT_TIMESTAMP?

• To ensure the time zone is consistent, it’s recommended to store the time zone in the database (e.g., a column of type TIMESTAMP WITH TIME ZONE) or use a fixed time zone for all session queries.

 

11. How can I get the current timestamp with a specific time zone offset?

• You can adjust the session’s time zone or use the FROM_TZ function to convert a TIMESTAMP to a specific time zone:

SELECT FROM_TZ(CURRENT_TIMESTAMP, 'UTC') AT TIME ZONE 'America/New_York' FROM dual;

 

12. Can I store CURRENT_TIMESTAMP in a table?

• Yes, you can store the result of CURRENT_TIMESTAMP in a table. The column should be of type TIMESTAMP WITH TIME ZONE. For example:

CREATE TABLE event_log (

    event_id NUMBER,

    event_description VARCHAR2(255),

    event_time TIMESTAMP WITH TIME ZONE

);

 

INSERT INTO event_log (event_id, event_description, event_time)

VALUES (1, 'User logged in', CURRENT_TIMESTAMP);

 

13. Can CURRENT_TIMESTAMP be used in calculations or arithmetic?

• Yes, you can perform date arithmetic with CURRENT_TIMESTAMP. For example:
• Adding days:

SELECT CURRENT_TIMESTAMP + INTERVAL '5' DAY FROM dual;

• Subtracting hours:

SELECT CURRENT_TIMESTAMP - INTERVAL '3' HOUR FROM dual;

 

14. How do I format CURRENT_TIMESTAMP?

• You can use the TO_CHAR function to format CURRENT_TIMESTAMP to a specific date and time format. For example:

SELECT TO_CHAR(CURRENT_TIMESTAMP, 'YYYY-MM-DD HH24:MI:SS') FROM dual;

 

15. What happens if I run CURRENT_TIMESTAMP in different time zones?

• If you change the session’s time zone (e.g., from UTC to America/New_York), the value of CURRENT_TIMESTAMP will change to reflect the new time zone.

 

16. How do I get the current timestamp in UTC?

• You can retrieve the current timestamp in UTC with the following query:

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