CURRENT_DATE FAQS

 1. What is CURRENT_DATE in Oracle?

• CURRENT_DATE is a built-in function in Oracle that returns the current date and time according to the session’s time zone. Unlike SYSDATE, which returns the system time of the database server, CURRENT_DATE reflects the session’s time zone settings.

 

2. What data type does CURRENT_DATE return?

• CURRENT_DATE returns a DATE data type, which includes both the date and time (in DD-MON-YY HH24:MI:SS format by default).

 

3. How is CURRENT_DATE different from SYSDATE?

• SYSDATE returns the current date and time based on the database server's system clock.
• CURRENT_DATE returns the current date and time based on the session's time zone. This means that if your session is in a different time zone, CURRENT_DATE will return a different result from SYSDATE.

 

4. How can I get the current date in CURRENT_DATE without the time?

• You can extract just the date part (without the time) by using the TRUNC function:

SELECT TRUNC(CURRENT_DATE) FROM dual;

 

5. How do I change the time zone for CURRENT_DATE?

• You can change the time zone for your session using the ALTER SESSION command. For example, to set the session's time zone to UTC:

·        ALTER SESSION SET TIME_ZONE = 'UTC';

After this, CURRENT_DATE will return the current date and time in the UTC time zone.

 

6. Does CURRENT_DATE reflect daylight saving time?

• Yes, CURRENT_DATE takes daylight saving time into account, as it reflects the current time in the session’s time zone, which may be adjusted for daylight saving time depending on the region.

 

7. Can I perform arithmetic operations with CURRENT_DATE?

• Yes, you can perform date arithmetic with CURRENT_DATE. For example:
• Adding 5 days:

SELECT CURRENT_DATE + 5 FROM dual;

• Subtracting 3 days:

SELECT CURRENT_DATE - 3 FROM dual;

 

8. What happens if I run CURRENT_DATE in a different time zone?

• The result of CURRENT_DATE will depend on the time zone setting of your session. If the session’s time zone is set to a different region, CURRENT_DATE will return the date and time for that region.

 

9. How do I get the current timestamp with time zone information?

• To get the current timestamp with time zone information, you can use SYSTIMESTAMP, which returns a TIMESTAMP WITH TIME ZONE data type:

SELECT SYSTIMESTAMP FROM dual;

 

10. Can I use CURRENT_DATE in WHERE clauses to filter records by the current date?

• Yes, you can use CURRENT_DATE in WHERE clauses to filter records based on the current date and time in your session’s time zone. For example:

SELECT * FROM orders

WHERE order_date >= CURRENT_DATE;

 

11. Can CURRENT_DATE change during query execution?

• Yes, CURRENT_DATE can change if the query runs for a long time. It’s a non-deterministic function that gets evaluated every time it’s called, so if the query takes a significant amount of time, the time returned by CURRENT_DATE may differ from the time when the query started.

 

12. How do I get the session’s time zone?

• You can check the current session's time zone using the following query:

SELECT sessiontimezone FROM dual;

 

13. Is CURRENT_DATE affected by the ALTER SESSION command?

• Yes, the ALTER SESSION command changes the session’s time zone, which will directly affect the result of CURRENT_DATE since it returns the current date and time based on the session’s time zone.

 

14. How do I compare CURRENT_DATE with a date column in a table?

• You can use CURRENT_DATE to compare the current date with a column in a table. For example, to find records where the order date is today:

SELECT * FROM orders

WHERE TRUNC(order_date) = TRUNC(CURRENT_DATE);

 

15. Can CURRENT_DATE be used in calculations?

• Yes, you can use CURRENT_DATE in calculations. For example, you can subtract a date column from CURRENT_DATE to calculate the difference in days:

SELECT CURRENT_DATE - hire_date AS days_since_hire FROM employees;

 

16. What is the performance impact of using CURRENT_DATE in large queries?

• Since CURRENT_DATE is non-deterministic and can change with each execution, it might cause performance issues when used in large queries that need to be executed multiple times or in complex joins. For consistent results, it is advisable to store the value of CURRENT_DATE in a variable and use that in the query.