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| author | Bruce Momjian <bruce@momjian.us> | 2014-09-05 18:59:41 -0400 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2014-09-05 18:59:41 -0400 |
| commit | 1f4d1074c5d83a682e71104114211f6ddee129a5 (patch) | |
| tree | a26c99f80fd49315ec6d92fe325d03513e125a76 /doc/src/sgml/ref | |
| parent | a9c22d1480aa8e6d97a000292d05ef2b31bbde4e (diff) | |
| download | postgresql-1f4d1074c5d83a682e71104114211f6ddee129a5.tar.gz postgresql-1f4d1074c5d83a682e71104114211f6ddee129a5.zip | |
Clarify documentation about "peer" rows in window functions
Peer rows are matching rows when ORDER BY is specified.
Report by arnaud.mouronval@gmail.com, David G Johnston
Diffstat (limited to 'doc/src/sgml/ref')
| -rw-r--r-- | doc/src/sgml/ref/select.sgml | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml index b69b63494b8..940d1aa5c0d 100644 --- a/doc/src/sgml/ref/select.sgml +++ b/doc/src/sgml/ref/select.sgml @@ -792,8 +792,9 @@ UNBOUNDED FOLLOWING The default framing option is <literal>RANGE UNBOUNDED PRECEDING</>, which is the same as <literal>RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW</>; it sets the frame to be all rows from the partition start - up through the current row's last peer in the <literal>ORDER BY</> - ordering (which means all rows if there is no <literal>ORDER BY</>). + up through the current row's last peer (a row that <literal>ORDER + BY</> considers equivalent to the current row, or all rows if there + is no <literal>ORDER BY</>). In general, <literal>UNBOUNDED PRECEDING</> means that the frame starts with the first row of the partition, and similarly <literal>UNBOUNDED FOLLOWING</> means that the frame ends with the last @@ -817,7 +818,7 @@ UNBOUNDED FOLLOWING results if the <literal>ORDER BY</> ordering does not order the rows uniquely. The <literal>RANGE</> options are designed to ensure that rows that are peers in the <literal>ORDER BY</> ordering are treated - alike; any two peer rows will be both in or both not in the frame. + alike; all peer rows will be in the same frame. </para> <para> |