diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/func.sgml | 34 |
1 files changed, 23 insertions, 11 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 19d35765178..139c81effc3 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.196 2004/03/30 15:53:18 momjian Exp $ +$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.197 2004/04/10 18:02:59 momjian Exp $ PostgreSQL documentation --> @@ -4948,18 +4948,31 @@ EXTRACT (<replaceable>field</replaceable> FROM <replaceable>source</replaceable> <term><literal>century</literal></term> <listitem> <para> - The year field divided by 100 + The historical definition of a century. </para> <screen> -SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40'); +SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13'); <lineannotation>Result: </lineannotation><computeroutput>20</computeroutput> +SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40'); +<lineannotation>Result: </lineannotation><computeroutput>21</computeroutput> </screen> <para> - Note that the result for the century field is simply the year field - divided by 100, and not the conventional definition which puts most - years in the 1900's in the twentieth century. + An historical century is a period of 100 years. + The first century starts at 0001-01-01 00:00:00 AD, although + they did not know at the time. This definition applies to all + Gregorian calendar countries. There is no number 0 century, + you go from -1 to 1. + + If you disagree with this, please write your complaint to: + Pope, Cathedral Saint-Peter of Roma, Vatican. + </para> + + <para> + Compatibility: if you want the previous postgres version of century, + just divide the year by 100. Note that with this definition, + century number 0 lasts 200 years. </para> </listitem> </varlistentry> @@ -5083,18 +5096,17 @@ SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5'); <term><literal>millennium</literal></term> <listitem> <para> - The year field divided by 1000 + The conventional historical millennium. </para> <screen> SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40'); -<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput> +<lineannotation>Result: </lineannotation><computeroutput>3</computeroutput> </screen> <para> - Note that the result for the millennium field is simply the year field - divided by 1000, and not the conventional definition which puts - years in the 1900's in the second millennium. + Years in the 1900's are in the second millennium. + The third millennium starts January 1, 2001. </para> </listitem> </varlistentry> |