@@ -1257,6 +1257,12 @@ SELECT 3 OPERATOR(pg_catalog.+) 4;
12571257 </para>
12581258 </listitem>
12591259
1260+ <listitem>
1261+ <para>
1262+ A collation expression
1263+ </para>
1264+ </listitem>
1265+
12601266 <listitem>
12611267 <para>
12621268 A scalar subquery
@@ -1898,8 +1904,8 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
18981904 </note>
18991905 </sect2>
19001906
1901- <sect2 id="sql-syntax-collate-clause ">
1902- <title>COLLATE Clause </title>
1907+ <sect2 id="sql-syntax-collate-exprs ">
1908+ <title>Collation Expressions </title>
19031909
19041910 <indexterm>
19051911 <primary>COLLATE</primary>
@@ -1925,7 +1931,7 @@ CAST ( <replaceable>expression</replaceable> AS <replaceable>type</replaceable>
19251931 </para>
19261932
19271933 <para>
1928- The twotypical uses of the <literal>COLLATE</literal> clause are
1934+ The twocommon uses of the <literal>COLLATE</literal> clause are
19291935 overriding the sort order in an <literal>ORDER BY</> clause, for
19301936 example:
19311937<programlisting>
@@ -1934,15 +1940,28 @@ SELECT a, b, c FROM tbl WHERE ... ORDER BY a COLLATE "C";
19341940 and overriding the collation of a function or operator call that
19351941 has locale-sensitive results, for example:
19361942<programlisting>
1937- SELECT * FROM tbl WHERE a > 'foo' COLLATE "C";
1943+ SELECT * FROM tbl WHERE a > 'foo' COLLATE "C";
1944+ </programlisting>
1945+ Note that in the latter case the <literal>COLLATE</> clause is
1946+ attached to an input argument of the operator we wish to affect.
1947+ It doesn't matter which argument of the operator or function call the
1948+ <literal>COLLATE</> clause is attached to, because the collation that is
1949+ applied by the operator or function is derived by considering all
1950+ arguments, and an explicit <literal>COLLATE</> clause will override the
1951+ collations of all other arguments. (Attaching non-matching
1952+ <literal>COLLATE</> clauses to more than one argument, however, is an
1953+ error. For more details see <xref linkend="collation">.)
1954+ Thus, this gives the same result as the previous example:
1955+ <programlisting>
1956+ SELECT * FROM tbl WHERE a COLLATE "C" > 'foo';
1957+ </programlisting>
1958+ But this is an error:
1959+ <programlisting>
1960+ SELECT * FROM tbl WHERE (a > 'foo') COLLATE "C";
19381961</programlisting>
1939- In the latter case it doesn't matter which argument of the
1940- operator of function call the <literal>COLLATE</> clause is
1941- attached to, because the collation that is applied by the operator
1942- or function is derived from all arguments, and
1943- the <literal>COLLATE</> clause will override the collations of all
1944- other arguments. Attaching nonmatching <literal>COLLATE</>
1945- clauses to more than one argument, however, is an error.
1962+ because it attempts to apply a collation to the result of the
1963+ <literal>></> operator, which is of the non-collatable data type
1964+ <type>boolean</>.
19461965 </para>
19471966 </sect2>
19481967