@@ -2688,19 +2688,6 @@ P <optional> <replaceable>years</>-<replaceable>months</>-<replaceable>days</> <
26882688 to each field if any field is negative.
26892689 </para>
26902690
2691- <para>
2692- Internally <type>interval</> values are stored as months, days,
2693- and seconds. This is done because the number of days in a month
2694- varies, and a day can have 23 or 25 hours if a daylight savings
2695- time adjustment is involved. The months and days fields are integers
2696- while the seconds field can store fractions. Because intervals are
2697- usually created from constant strings or <type>timestamp</> subtraction,
2698- this storage method works well in most cases. Functions
2699- <function>justify_days</> and <function>justify_hours</> are
2700- available for adjusting days and hours that overflow their normal
2701- ranges.
2702- </para>
2703-
27042691 <para>
27052692 In the verbose input format, and in some fields of the more compact
27062693 input formats, field values can have fractional parts; for example
@@ -2752,6 +2739,33 @@ P <optional> <replaceable>years</>-<replaceable>months</>-<replaceable>days</> <
27522739 </tgroup>
27532740 </table>
27542741
2742+ <para>
2743+ Internally <type>interval</type> values are stored as months, days,
2744+ and seconds. This is done because the number of days in a month
2745+ varies, and a day can have 23 or 25 hours if a daylight savings
2746+ time adjustment is involved. The months and days fields are integers
2747+ while the seconds field can store fractions. Because intervals are
2748+ usually created from constant strings or <type>timestamp</type> subtraction,
2749+ this storage method works well in most cases, but can cause unexpected
2750+ results:
2751+
2752+ <programlisting>
2753+ SELECT EXTRACT(hours from '80 minutes'::interval);
2754+ date_part
2755+ -----------
2756+ 1
2757+
2758+ SELECT EXTRACT(days from '80 hours'::interval);
2759+ date_part
2760+ -----------
2761+ 0
2762+ </programlisting>
2763+
2764+ Functions <function>justify_days</function> and
2765+ <function>justify_hours</function> are available for adjusting days
2766+ and hours that overflow their normal ranges.
2767+ </para>
2768+
27552769 </sect2>
27562770
27572771 <sect2 id="datatype-interval-output">