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<chapter id="functions">

<title>Functions and Operators</title>

</para>

<screen>

SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-08');

<lineannotation>Result: </lineannotation><computeroutput>982384720</computeroutput>

SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08');

<lineannotation>Result: </lineannotation><computeroutput>982384720.12</computeroutput>

SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');

<lineannotation>Result: </lineannotation><computeroutput>442800</computeroutput>

Here is how you can convert an epoch value back to a time

stamp:

</para>

<screen>

SELECT TIMESTAMP WITH TIME ZONE 'epoch' + 982384720 * INTERVAL '1 second';

SELECT TIMESTAMP WITH TIME ZONE 'epoch' + 982384720.12 * INTERVAL '1 second';

</screen>

<para>

(The <function>to_timestamp</> function encapsulates the above

conversion.)

</para>

</listitem>

</varlistentry>