Introduction to Oracle TIMESTAMP WITH LOCAL TIME ZONE Data Type

Oracle TIMESTAMP WITH LOCAL TIME ZONE is a data type for date and time information that includes time zone information. Unlike the TIMESTAMP data type, it automatically converts timestamps to the local time of the database server’s time zone. Therefore, when using TIMESTAMP WITH LOCAL TIME ZONE, you do not need to consider time zone differences between the application and the database server, making it ideal for applications that span multiple time zones.

Syntax

The syntax for creating a column or variable of type TIMESTAMP WITH LOCAL TIME ZONE is as follows:

column_name TIMESTAMP( [fractional_seconds_precision] ) WITH LOCAL TIME ZONE

Where fractional_seconds_precision parameter specifies the number of decimal digits to be stored, ranging from 0 to 9, with a default value of 6.

Use Cases

TIMESTAMP WITH LOCAL TIME ZONE data type is commonly used in applications that require handling of time zones, such as global e-commerce websites, international flight booking systems, and so on. It helps applications to avoid time zone issues and ensures accurate handling of date and time information across multiple time zones.

Examples

Example 1

Let’s assume there is a table orders that contains order ID (order_id) and order time (order_time) as two fields, where order time is of TIMESTAMP WITH LOCAL TIME ZONE data type. We can create this table using the following SQL statement:

CREATE TABLE orders (
  order_id NUMBER,
  order_time TIMESTAMP WITH LOCAL TIME ZONE
);

Now, we can insert some data:

INSERT INTO orders VALUES (1, TO_TIMESTAMP_TZ('2022-04-03 09:30:00 -08:00', 'YYYY-MM-DD HH24:MI:SS TZH:TZM'));
INSERT INTO orders VALUES (2, TO_TIMESTAMP_TZ('2022-04-03 12:45:00 -05:00', 'YYYY-MM-DD HH24:MI:SS TZH:TZM'));
INSERT INTO orders VALUES (3, TO_TIMESTAMP_TZ('2022-04-03 18:00:00 +02:00', 'YYYY-MM-DD HH24:MI:SS TZH:TZM'));

These data represent order times in three different time zones. Now, if we want to query the order time for order ID 1, we can use the following SQL statement:

SELECT order_time FROM orders WHERE order_id = 1;

This query will return the local time value of the order time, for example, the local time value in the US Pacific time zone would be 03-APR-22 09.30.00.000000 AM -07:00.

Example 2

Suppose you need to query the occurrence time of an event in different time zones, you can use the following statement:

SELECT event_name, start_time AT TIME ZONE 'US/Pacific' AS start_time_pst,
       start_time AT TIME ZONE 'Europe/London' AS start_time_gmt
FROM events
WHERE event_name = 'Some Event';

This statement will query the “Some Event” with the occurrence time of “2022-03-15 12:30:00” in the events table, and convert it to US Pacific Time and Greenwich Mean Time. The query result is as follows:

EVENT_NAME  START_TIME_PST            START_TIME_GMT
----------- ------------------------ ------------------------
Some Event  15-MAR-22 12.30.00.000000 15-MAR-22 20.30.00.000000

In this example, the AT TIME ZONE clause converts the start_time column from the local time stored in the database to the specified time zone. In the result, the start_time_pst column displays the US Pacific Time, while the start_time_gmt column displays the Greenwich Mean Time.

By using the TIMESTAMP WITH LOCAL TIME ZONE data type and the AT TIME ZONE clause, Oracle database can easily convert time from one time zone to another, making it more convenient for handling cross-time zone data.

Conclusion

The TIMESTAMP WITH LOCAL TIME ZONE data type can store date and time data with time zone information, making it more convenient for handling cross-time zone data in the database. The AT TIME ZONE clause can convert data from one time zone to another, further enhancing the flexibility and efficiency of the database in handling cross-time zone data.