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Improve our explanation of the OVERLAPS operator. 

Per gripe from Frank van Vugt.
This commit is contained in:
Tom Lane 2010-06-05 14:56:36 +00:00
parent 98e4005efb
commit 2944e6ecb6
1 changed files with 16 additions and 2 deletions
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18
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.516 2010/06/03 14:40:42 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.517 2010/06/05 14:56:36 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -6155,7 +6155,15 @@ SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
This expression yields true when two time periods (defined by their
endpoints) overlap, false when they do not overlap. The endpoints
can be specified as pairs of dates, times, or time stamps; or as
a date, time, or time stamp followed by an interval.
a date, time, or time stamp followed by an interval. When a pair
of values is provided, either the start or the end can be written
first; <literal>OVERLAPS</> automatically takes the earlier value
of the pair as the start. Each time period is considered to
represent the half-open interval <replaceable>start</> <literal>&lt;=</>
<replaceable>time</> <literal>&lt;</> <replaceable>end</>, unless
<replaceable>start</> and <replaceable>end</> are equal in which case it
represents that single time instant. This means for instance that two
time periods with only an endpoint in common do not overlap.
</para>
<screen>
@ -6165,6 +6173,12 @@ SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
(DATE '2001-10-30', DATE '2002-10-30');
<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS
(DATE '2001-10-30', DATE '2001-10-31');
<lineannotation>Result: </lineannotation><computeroutput>false</computeroutput>
SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS
(DATE '2001-10-30', DATE '2001-10-31');
<lineannotation>Result: </lineannotation><computeroutput>true</computeroutput>
</screen>
<para>