How to change system date in Oracle

Title: How Oracle changes the system date, with detailed code examples

In the Oracle database, the system date is a very important element, which determines the date in the database. Behavior of time functions and date operations. Sometimes, in a test environment or under specific circumstances, we may need to manually change the system date for debugging or verification. This article will introduce how to change the system date in the Oracle database and provide specific code examples for reference.

1. Use the ALTER SYSTEM command to change the database date

In the Oracle database, you can use the ALTER SYSTEM command to change the system date of the database. The specific steps are as follows:

ALTER SYSTEM SET TIME_ZONE = 'UTC';

The above command sets the system time zone to UTC standard time. You can also set the time to another time zone as needed, or adjust the system date by changing the date directly.

2. Use the DBMS_SCHEDULER package to change the database date

Another way to change the system date is to use the DBMS_SCHEDULER package provided by Oracle. Change the system date by creating a scheduled task and executing the task regularly to change the system date. The following is a specific code example:

BEGIN
    DBMS_SCHEDULER.CREATE_JOB (
        job_name        => 'CHANGE_DATE_JOB',
        job_type        => 'PLSQL_BLOCK',
        job_action      => 'BEGIN EXECUTE IMMEDIATE ''ALTER SESSION SET NLS_DATE_FORMAT = ''DD-MON-YYYY HH24:MI:SS''''; END;',
        start_date      => SYSTIMESTAMP,
        repeat_interval => 'FREQ=DAILY; INTERVAL=1',
        end_date        => SYSTIMESTAMP + INTERVAL '1' DAY
    );
    
    DBMS_SCHEDULER.ENABLE('CHANGE_DATE_JOB');
END;
/

The above code creates a scheduled task CHANGE_DATE_JOB, which is executed repeatedly every day and changes the date format of the system date to 'DD-MON-YYYY HH24:MI: SS', you can change the date format and execution frequency as needed.

3. Use the BEFORE TRIGGER trigger to change the database date

You can also use the BEFORE TRIGGER trigger to implement the function of changing the system date when a specific operation is triggered. The following is a sample code:

CREATE OR REPLACE TRIGGER update_date_trigger
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN
    :NEW.created_date := SYSTIMESTAMP;
END;
/

The above code creates a BEFORE INSERT trigger. When data is inserted into the my_table table, the created_date field is automatically updated to the current system date and time.

Summary

Through the above introduction, we have learned about several methods of changing the system date in the Oracle database, including using the ALTER SYSTEM command, the DBMS_SCHEDULER package and the BEFORE TRIGGER trigger. Each method has its applicable scenarios and usage restrictions. You can choose the appropriate method to change the system date according to your specific needs.

I hope the code examples provided in this article can help you successfully change the system date in the Oracle database and achieve your specific needs.

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