MySQL UNIX_TIMESTAMP for PostgreSQL

Basic开发者_高级运维ally I am trying to convert a date field from my database into a number of seconds old. I used UNIX_TIMESTAMP on our old MySQL database and am looking for an equivalent function in PostgreSQL.

Thanks in advance

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SELECT extract(epoch FROM your_datetime_column)
FROM your_table

More details in the manual:

http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

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This:

select CURRENT_TIMESTAMP - '1970-01-01';

Will give you an interval type. You can get seconds out of that interval result if you need it.

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I am trying to convince existing MySQL queries to work, this is what I have, seem to be working fine to me.

CREATE OR REPLACE FUNCTION UNIX_TIMESTAMP(date_field timestamp with time zone) RETURNS integer 
AS $$
BEGIN
    RETURN extract(epoch FROM date_field);
END;
$$ LANGUAGE plpgsql;