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Overview

The UNIX_SECONDS() function returns a given timestamp to a UNIX timestamp in seconds, from 1970-01-01 00:00:00-00. Its syntax is illustrated below: 
SELECT UNIX_SECONDS(TIMESTAMP)
Its input type is a TIMESTAMP expression, and the return data type is BIGINT representing time in seconds.

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Examples

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Case #1: Basic UNIX_SECONDS() function

The below example uses the UNIX_SECONDS() function to convert a given timestamp into a UNIX timestamp in seconds: 
SELECT UNIX_SECONDS(TIMESTAMP "2008-12-25 15:30:00+00") AS unix_secondsvalues;
The final output will be as follows: 
+-----------------------------+
| unix_secondsvalues          |
+-----------------------------+
| 1230219000.000000           |
+-----------------------------+

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Case #2: UNIX_SECONDS() function using columns

Let’s suppose we have a table named **time_example **with the following timestamp values in the time_stampvalues column: 
CREATE TABLE time_example (
  time_stampvalues timestamp
);

INSERT INTO time_example VALUES 
('2022-12-25 13:30:00'),
('2020-09-25 07:25:00'),
('2008-12-25 15:30:00'),
('2021-10-02 06:30:00');

SELECT * FROM time_example;
The above query will return the following table: 
+-------------------------+
| time_stampvalues        | 
+-------------------------+
| 2022-12-25 13:30:00     |
| 2020-09-25 07:25:00     |
| 2008-12-25 15:30:00     |
| 2021-10-02 06:30:00     | 
+-------------------------+
  1. We want to convert all timestamp values into UNIX timestamp values in seconds. To do that, we have to run the following query:
SELECT time_stampvalues, UNIX_SECONDS(time_stampvalues)
AS time_secondsvalues
FROM time_example;
  1. The output displays all the timestamp entries of the table in the time_stampvalues column and the converted UNIX seconds timestamp entries in the column time_secondsvalues.
+-------------------------+-----------------------+
| time_stampvalues        | time_secondsvalues    |
+-------------------------+-----------------------+
| 2022-12-25 13:30:00     | 1671975000.000000     |
| 2020-09-25 07:25:00     | 1601018700.000000     |
| 2008-12-25 15:30:00     | 1230219000.000000     |
| 2021-10-02 06:30:00     | 1633156200.000000     |
+-------------------------+-----------------------+