Improve documentation of EXTRACT(WEEK).
The docs showed that early-January dates can be considered part of the previous year for week-counting purposes, but failed to say explicitly that late-December dates can also be considered part of the next year. Fix that, and add a cross-reference to the "isoyear" field. Per bug #7967 from Pawel Kobylak.
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@ -7151,16 +7151,19 @@ SELECT EXTRACT(SECOND FROM TIME '17:12:28.5');
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<listitem>
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<listitem>
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<para>
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<para>
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The number of the week of the year that the day is in. By definition
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The number of the week of the year that the day is in. By definition
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(<acronym>ISO</acronym> 8601), the first week of a year
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(<acronym>ISO</acronym> 8601), weeks start on Mondays and the first
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contains January 4 of that year. (The <acronym>ISO</acronym>-8601
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week of a year contains January 4 of that year. In other words, the
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week starts on Monday.) In other words, the first Thursday of
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first Thursday of a year is in week 1 of that year.
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a year is in week 1 of that year.
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</para>
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</para>
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<para>
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<para>
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Because of this, it is possible for early January dates to be part of the
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In the ISO definition, it is possible for early-January dates to be
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52nd or 53rd week of the previous year. For example, <literal>2005-01-01</>
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part of the 52nd or 53rd week of the previous year, and for
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is part of the 53rd week of year 2004, and <literal>2006-01-01</> is part of
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late-December dates to be part of the first week of the next year.
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the 52nd week of year 2005.
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For example, <literal>2005-01-01</> is part of the 53rd week of year
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2004, and <literal>2006-01-01</> is part of the 52nd week of year
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2005, while <literal>2012-12-31</> is part of the first week of 2013.
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It's recommended to use the <literal>isoyear</> field together with
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<literal>week</> to get consistent results.
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</para>
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</para>
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<screen>
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<screen>
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