How to Get Epoch/UNIX Timestamp in PostgreSQL

In PostgreSQL, you can get Epoch timestamps using various date and time functions. This article explores different ways to retrieve Epoch timestamps in PostgreSQL and provides practical use cases.

Using the EXTRACT() Function

In PostgreSQL, you can use the EXTRACT() function to fetch the current Epoch timestamp. This function takes a field and an interval as arguments and returns the current timestamp in seconds since the Epoch.

Example SQL Query

To obtain the current Epoch timestamp using the EXTRACT() function, execute the following SQL query in your PostgreSQL database:

SELECT EXTRACT(EPOCH FROM CURRENT_TIMESTAMP) AS current_epoch_timestamp;

The above query will return the current Epoch timestamp as the result, labeled as "current_epoch_timestamp."

Use Case 1: Logging Timestamps

To log data with timestamps, you can use the EXTRACT() function to obtain the current timestamp and insert it into a database table. Here's an example SQL query:

INSERT INTO sensor_data (data, timestamp)
VALUES ('Sensor data reading...', EXTRACT(EPOCH FROM CURRENT_TIMESTAMP));

In this SQL query, we're inserting sensor data along with the current Epoch timestamp into a table called "sensor_data."

Use Case 2: Time Duration Calculation

If you need to measure the time taken for a task, you can use the EXTRACT() function to record start and end times. Here's how you can calculate the time elapsed in seconds:

INSERT INTO task_log (start_time, task_description) VALUES (EXTRACT(EPOCH FROM CURRENT_TIMESTAMP), 'Task started');

-- Perform a task or operation

UPDATE task_log SET end_time = EXTRACT(EPOCH FROM CURRENT_TIMESTAMP) WHERE task_description = 'Task started';

SELECT end_time - start_time AS time_elapsed_seconds FROM task_log WHERE task_description = 'Task started';

This SQL script records the start time when a task begins, and the end time when it ends using the EXTRACT() function. It then calculates the time elapsed in seconds by subtracting the start time from the end time.

Use Case 3: Expiry Timestamp for Cache

If you need to set an expiry timestamp for cache data, you can use the EXTRACT() function to calculate the expiry time based on the current timestamp. Here's an example SQL query:

INSERT INTO cached_data (data, expiry_timestamp)
VALUES ('Cached data...', EXTRACT(EPOCH FROM CURRENT_TIMESTAMP) + 600);

In this SQL query, the current Epoch timestamp is obtained using EXTRACT(), and then 600 seconds (10 minutes) are added to it to determine the cache expiry time. The data is inserted into a table called "cached_data."

Use Case 4: Event Scheduling

To schedule an event to occur in the future, you can use the EXTRACT() function to calculate the event time. Here's an example SQL script:

INSERT INTO event_schedule (event_description, event_timestamp)
VALUES ('Event scheduled for 1 hour from now', EXTRACT(EPOCH FROM CURRENT_TIMESTAMP) + 3600);

-- Wait for the event to occur

SELECT * FROM event_schedule WHERE event_timestamp <= EXTRACT(EPOCH FROM CURRENT_TIMESTAMP);

This SQL script calculates the event time as one hour from the current time and inserts it into a table called "event_schedule." It then waits for the event to occur by checking for events with timestamps less than or equal to the current timestamp.

These code examples illustrate how to get Epoch/UNIX timestamps in PostgreSQL and showcase their applications in practical scenarios. Whether you need to log data with timestamps, calculate time durations, set cache expiry times, or schedule events, Epoch timestamps are useful tools in PostgreSQL for time-related operations.