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Doc: update documentation for requirement of ORDER BY in GROUPS mode.
Commit ff4f88916
adjusted the code to enforce the SQL spec's requirement
that a window using GROUPS mode must have an ORDER BY clause. But I missed
that the documentation explicitly said you didn't have to have one.
Also minor wordsmithing in the window-function section of select.sgml.
Per Masahiko Sawada, though I didn't use his patch.
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@ -901,8 +901,8 @@ EXCLUDE NO OTHERS
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CURRENT ROW</literal>; it sets the frame to be all rows from the partition start
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up through the current row's last <firstterm>peer</firstterm> (a row
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that the window's <literal>ORDER BY</literal> clause considers
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equivalent to the current row), or all rows if there
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is no <literal>ORDER BY</literal>.
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equivalent to the current row; all rows are peers if there
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is no <literal>ORDER BY</literal>).
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In general, <literal>UNBOUNDED PRECEDING</literal> means that the frame
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starts with the first row of the partition, and similarly
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<literal>UNBOUNDED FOLLOWING</literal> means that the frame ends with the last
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@ -924,7 +924,7 @@ EXCLUDE NO OTHERS
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is an integer indicating that the frame starts or ends that many peer
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groups before or after the current row's peer group, where
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a <firstterm>peer group</firstterm> is a group of rows that are
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equivalent according to <literal>ORDER BY</literal>.
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equivalent according to the window's <literal>ORDER BY</literal> clause.
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In <literal>RANGE</literal> mode, use of
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an <replaceable>offset</replaceable> option requires that there be
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exactly one <literal>ORDER BY</literal> column in the window definition.
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@ -1917,8 +1917,8 @@ EXCLUDE NO OTHERS
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ends the specified number of <firstterm>peer groups</firstterm>
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before or after the current row's peer group, where a peer group is a
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set of rows that are equivalent in the <literal>ORDER BY</literal>
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ordering. (If there is no <literal>ORDER BY</literal>, the whole
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partition is one peer group.)
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ordering. (There must be an <literal>ORDER BY</literal> clause
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in the window definition to use <literal>GROUPS</literal> mode.)
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</para>
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</listitem>
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<listitem>
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