doc: Add example file for COPY

The paragraph for introducing INSERT and COPY discussed how a file could be used for bulk loading with COPY, without actually showing what the file would look like. This adds a programlisting for the file contents. Backpatch to all supported branches since this example has lacked the file contents since PostgreSQL 7.2. Author: Daniel Gustafsson <daniel@yesql.se> Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/158017814191.19852.15019251381150731439@wrigleys.postgresql.org Backpatch-through: 13

Author: danielgustafsson

doc/src/sgml/query.sgml

@@ -264,8 +264,18 @@ COPY weather FROM '/home/user/weather.txt';
 
  where the file name for the source file must be available on the
  machine running the backend process, not the client, since the backend process
- reads the file directly. You can read more about the
- <command>COPY</command> command in <xref linkend="sql-copy"/>.
+ reads the file directly. The data inserted above into the weather table
+ could also be inserted from a file containing (values are separated by a
+ tab character):
+
+<programlisting>
+San Francisco 46 50 0.25 1994-11-27
+San Francisco 43 57 0.0 1994-11-29
+Hayward 37 54 \N 1994-11-29
+</programlisting>
+
+ You can read more about the <command>COPY</command> command in
+ <xref linkend="sql-copy"/>.
  </para>
  </sect1>