提交 b548cde1 编写于 作者: T Tom Lane

Some more small improvements in response to 7.4 interactive docs comments.

上级 8afe005f
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.28 2005/01/05 14:22:39 petere Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.29 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -157,6 +157,20 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable>table_name
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Create a new table <literal>films_recent</literal> consisting of only
recent entries from the table <literal>films</literal>:
<programlisting>
CREATE TABLE films_recent AS
SELECT * FROM films WHERE date_prod &gt;= '2002-01-01';
</programlisting>
</para>
</refsect1>
<refsect1>
<title>Compatibility</title>
......
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.21 2005/01/04 00:39:53 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.22 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -100,6 +100,33 @@ DELETE <replaceable class="parameter">count</replaceable>
</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
<productname>PostgreSQL</productname> lets you reference columns of
other tables in the <literal>WHERE</> condition. For example, to
delete all films produced by a given producer, one might do
<programlisting>
DELETE FROM films
WHERE producer_id = producers.id AND producers.name = 'foo';
</programlisting>
What is essentially happening here is a join between <structname>films</>
and <structname>producers</>, with all successfully joined
<structname>films</> rows being marked for deletion.
This syntax is not standard. A more standard way to do it is
<programlisting>
DELETE FROM films
WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo');
</programlisting>
In some cases the join style is easier to write or faster to
execute than the sub-select style. One objection to the join style
is that there is no explicit list of what tables are being used,
which makes the style somewhat error-prone; also it cannot handle
self-joins.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
......@@ -122,7 +149,9 @@ DELETE FROM films;
<title>Compatibility</title>
<para>
This command conforms to the SQL standard.
This command conforms to the SQL standard, except that the ability to
reference other tables in the <literal>WHERE</> clause is a
<productname>PostgreSQL</productname> extension.
</para>
</refsect1>
</refentry>
......
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/drop_group.sgml,v 1.9 2005/01/04 00:39:53 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/drop_group.sgml,v 1.10 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -29,7 +29,7 @@ DROP GROUP <replaceable class="PARAMETER">name</replaceable>
<para>
<command>DROP GROUP</command> removes the specified group. The
users in the group are not deleted.
users in the group are not removed.
</para>
</refsect1>
......
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/insert.sgml,v 1.28 2005/01/04 00:39:53 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/insert.sgml,v 1.29 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -162,7 +162,7 @@ INSERT INTO films VALUES
</para>
<para>
In this second example, the <literal>len</literal> column is
In this example, the <literal>len</literal> column is
omitted and therefore it will have the default value:
<programlisting>
......@@ -172,7 +172,7 @@ INSERT INTO films (code, title, did, date_prod, kind)
</para>
<para>
The third example uses the <literal>DEFAULT</literal> clause for
This example uses the <literal>DEFAULT</literal> clause for
the date columns rather than specifying a value:
<programlisting>
......@@ -184,11 +184,20 @@ INSERT INTO films (code, title, did, date_prod, kind)
</para>
<para>
This example inserts several rows into table
<literal>films</literal> from table <literal>tmp</literal>:
To insert a row consisting entirely of default values:
<programlisting>
INSERT INTO films SELECT * FROM tmp;
INSERT INTO films DEFAULT VALUES;
</programlisting>
</para>
<para>
This example inserts some rows into table
<literal>films</literal> from a table <literal>tmp_films</literal>
with the same column layout as <literal>films</literal>:
<programlisting>
INSERT INTO films SELECT * FROM tmp_films WHERE date_prod &lt; '2004-05-07';
</programlisting>
</para>
......
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.32 2005/01/04 03:58:16 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select_into.sgml,v 1.33 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -105,6 +105,19 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Create a new table <literal>films_recent</literal> consisting of only
recent entries from the table <literal>films</literal>:
<programlisting>
SELECT * INTO films_recent FROM films WHERE date_prod &gt;= '2002-01-01';
</programlisting>
</para>
</refsect1>
<refsect1>
<title>Compatibility</title>
......@@ -120,6 +133,14 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replac
new code.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-createtableas" endterm="sql-createtableas-title"></member>
</simplelist>
</refsect1>
</refentry>
<!-- Keep this comment at the end of the file
......
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.31 2005/01/04 03:58:16 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.32 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
......@@ -114,8 +114,9 @@ UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> SET <replacea
expressions. This is similar to the list of tables that can be
specified in the <xref linkend="sql-from"
endterm="sql-from-title"> of a <command>SELECT</command>
statement; for example, an alias for the table name can be
specified.
statement. Note that the target table must not appear in the
<replaceable>fromlist</>, unless you intend a self-join (in which
case it must appear with an alias in the <replaceable>fromlist</>).
</para>
</listitem>
</varlistentry>
......@@ -154,10 +155,13 @@ UPDATE <replaceable class="parameter">count</replaceable>
<title>Notes</title>
<para>
When joining the target table to other tables using a <replaceable
class="PARAMETER">fromlist</replaceable>, be careful that the join
When a <literal>FROM</> clause is present, what essentially happens
is that the target table is joined to the tables mentioned in the
<replaceable>fromlist</replaceable>, and each output row of the join
represents an update operation for the target table. When using
<literal>FROM</> you should ensure that the join
produces at most one output row for each row to be modified. In
other words, a target row mustn't join to more than one row from
other words, a target row shouldn't join to more than one row from
the other table(s). If it does, then only one of the join rows
will be used to update the target row, but which one will be used
is not readily predictable.
......@@ -210,15 +214,18 @@ UPDATE employees SET sales_count = sales_count + 1 WHERE id =
</programlisting>
Attempt to insert a new stock item along with the quantity of stock. If
the item exists, update the stock count of the existing item. To do this,
use savepoints.
the item already exists, instead update the stock count of the existing
item. To do this without failing the entire transaction, use savepoints.
<programlisting>
BEGIN;
-- other operations
SAVEPOINT sp1;
INSERT INTO wines VALUES('Chateau Lafite 2003', '24');
-- Check for unique violation on name
-- Assume the above fails because of a unique key violation,
-- so now we issue these commands:
ROLLBACK TO sp1;
UPDATE wines SET stock = stock + 24 WHERE winename='Chateau Lafite 2003';
UPDATE wines SET stock = stock + 24 WHERE winename = 'Chateau Lafite 2003';
-- continue with other operations, and eventually
COMMIT;
</programlisting>
</para>
......@@ -228,10 +235,18 @@ COMMIT;
<title>Compatibility</title>
<para>
This command conforms to the <acronym>SQL</acronym> standard. The
<literal>FROM</literal> clause is a
This command conforms to the <acronym>SQL</acronym> standard, except
that the <literal>FROM</literal> clause is a
<productname>PostgreSQL</productname> extension.
</para>
<para>
Some other database systems offer a <literal>FROM</> option in which
the target table is supposed to be listed again within <literal>FROM</>.
That is not how <productname>PostgreSQL</productname> interprets
<literal>FROM</>. Be careful when porting applications that use this
extension.
</para>
</refsect1>
</refentry>
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册