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1 | | -<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.382 2007/06/06 23:00:35 tgl Exp $ --> |
| 1 | +<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.383 2007/07/18 03:12:42 momjian Exp $ --> |
2 | 2 |
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3 | 3 | <chapter id="functions"> |
4 | 4 | <title>Functions and Operators</title> |
@@ -5895,6 +5895,17 @@ SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS |
5895 | 5895 | <literal>CST7CDT</literal>. |
5896 | 5896 | </para> |
5897 | 5897 |
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| 5898 | + <para> |
| 5899 | + Note that when the <function>age</> function operates on multi-month |
| 5900 | + intervals, <productname>PostgreSQL</> adds days to the earlier date |
| 5901 | + until full months can be added. This yields a different result than |
| 5902 | + adding full months first if the interval crosses from one month to the |
| 5903 | + next. For example, <literal>age('2004-06-01', '2004-04-30')</> yeilds |
| 5904 | + <literal>1 mon 1 day</> using the <productname>PostgreSQL</> method, |
| 5905 | + while adding the month first would yield <literal>1 mon 2 days</> |
| 5906 | + because May has 31 days, while April has only 30. |
| 5907 | + </para> |
| 5908 | + |
5898 | 5909 | <sect2 id="functions-datetime-extract"> |
5899 | 5910 | <title><function>EXTRACT</function>, <function>date_part</function></title> |
5900 | 5911 |
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