mirror of
https://github.com/postgres/postgres.git
synced 2025-12-19 17:02:53 +03:00
Complete merge of all old man page information.
ecpg reference page still needs formatting.
This commit is contained in:
Thomas G. Lockhart
@@ -1,6 +1,11 @@
|
||||
<!--
|
||||
$Header: /cvsroot/pgsql/doc/src/sgml/ref/fetch.sgml,v 1.7 1999/07/22 15:09:12 thomas Exp $
|
||||
Postgres documentation
|
||||
-->
|
||||
|
||||
<refentry id="SQL-FETCH">
|
||||
<refmeta>
|
||||
<refentrytitle>
|
||||
<refentrytitle id="SQL-FETCH-TITLE">
|
||||
FETCH
|
||||
</refentrytitle>
|
||||
<refmiscinfo>SQL - Language Statements</refmiscinfo>
|
||||
@@ -15,7 +20,7 @@
|
||||
</refnamediv>
|
||||
<refsynopsisdiv>
|
||||
<refsynopsisdivinfo>
|
||||
<date>1998-09-01</date>
|
||||
<date>1999-07-20</date>
|
||||
</refsynopsisdivinfo>
|
||||
<synopsis>
|
||||
FETCH [ <replaceable class="PARAMETER">selector</replaceable> ] [ <replaceable class="PARAMETER">count</replaceable> ] { IN | FROM } <replaceable class="PARAMETER">cursor</replaceable>
|
||||
@@ -212,8 +217,9 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
<title>
|
||||
Description
|
||||
</title>
|
||||
|
||||
<para>
|
||||
FETCH allows a user to retrieve rows using a cursor.
|
||||
<command>FETCH</command> allows a user to retrieve rows using a cursor.
|
||||
The number of rows retrieved is specified by
|
||||
<replaceable class="PARAMETER">#</replaceable>.
|
||||
If the number of rows remaining in the cursor is less
|
||||
@@ -226,38 +232,13 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
|
||||
<tip>
|
||||
<para>
|
||||
Negative numbers are now allowed to be specified for the
|
||||
Negative numbers are allowed to be specified for the
|
||||
row count. A negative number is equivalent to reversing
|
||||
the sense of the FORWARD and BACKWARD keywords. For example,
|
||||
<command>FORWARD -1</command> is the same as <command>BACKWARD 1</command>.
|
||||
</para>
|
||||
</tip>
|
||||
</para>
|
||||
<para>
|
||||
Note that the FORWARD and BACKWARD keywords are
|
||||
<productname>Postgres</productname> extensions.
|
||||
The <acronym>SQL92</acronym> syntax is also supported, specified
|
||||
in the second form of the command. See below for details
|
||||
on compatibility issues.
|
||||
</para>
|
||||
<para>
|
||||
Once all rows are fetched, every other fetch access returns
|
||||
no rows.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Updating data in a cursor is not supported by
|
||||
<productname>Postgres</productname>,
|
||||
because mapping cursor updates back to base tables is
|
||||
not generally possible, as is also the case with VIEW updates.
|
||||
Consequently,
|
||||
users must issue explicit UPDATE commands to replace data.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Cursors may only be used inside of transactions because
|
||||
the data that they store spans multiple user queries.
|
||||
</para>
|
||||
|
||||
<refsect2 id="R2-SQL-FETCH-3">
|
||||
<refsect2info>
|
||||
@@ -266,11 +247,45 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
<title>
|
||||
Notes
|
||||
</title>
|
||||
|
||||
<para>
|
||||
Use <command>MOVE</command> to change cursor position.
|
||||
<command>DECLARE</command> will define a cursor.
|
||||
Refer to <command>BEGIN</command>, <command>COMMIT</command>, and
|
||||
<command>ROLLBACK</command>
|
||||
Note that the FORWARD and BACKWARD keywords are
|
||||
<productname>Postgres</productname> extensions.
|
||||
The <acronym>SQL92</acronym> syntax is also supported, specified
|
||||
in the second form of the command. See below for details
|
||||
on compatibility issues.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Once all rows are fetched, every other fetch access returns
|
||||
no rows.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Updating data in a cursor is not supported by
|
||||
<productname>Postgres</productname>,
|
||||
because mapping cursor updates back to base tables is
|
||||
not generally possible, as is also the case with VIEW updates.
|
||||
Consequently,
|
||||
users must issue explicit UPDATE commands to replace data.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Cursors may only be used inside of transactions because
|
||||
the data that they store spans multiple user queries.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Use
|
||||
<xref linkend="sql-move-title" endterm="sql-move-title">
|
||||
to change cursor position.
|
||||
<xref linkend="sql-declare-title" endterm="sql-declare-title">
|
||||
will define a cursor.
|
||||
Refer to
|
||||
<xref linkend="sql-begin-title" endterm="sql-begin-title">,
|
||||
<xref linkend="sql-commit-title" endterm="sql-commit-title">,
|
||||
and
|
||||
<xref linkend="sql-rollback-title" endterm="sql-rollback-title">
|
||||
for further information about transactions.
|
||||
</para>
|
||||
</refsect2>
|
||||
@@ -280,7 +295,10 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
<title>
|
||||
Usage
|
||||
</title>
|
||||
|
||||
<para>
|
||||
The following examples traverses a table using a cursor.
|
||||
|
||||
<programlisting>
|
||||
--set up and use a cursor:
|
||||
--
|
||||
@@ -292,6 +310,7 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
--
|
||||
FETCH FORWARD 5 IN liahona;
|
||||
|
||||
<computeroutput>
|
||||
code |title |did| date_prod|kind |len
|
||||
-----+-----------------------+---+----------+----------+------
|
||||
BL101|The Third Man |101|1949-12-23|Drama | 01:44
|
||||
@@ -299,15 +318,17 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
JL201|Une Femme est une Femme|102|1961-03-12|Romantic | 01:25
|
||||
P_301|Vertigo |103|1958-11-14|Action | 02:08
|
||||
P_302|Becket |103|1964-02-03|Drama | 02:28
|
||||
|
||||
</computeroutput>
|
||||
|
||||
--Fetch previous row:
|
||||
--
|
||||
FETCH BACKWARD 1 IN liahona;
|
||||
|
||||
<computeroutput>
|
||||
code |title |did| date_prod|kind |len
|
||||
-----+-----------------------+---+----------+----------+------
|
||||
P_301|Vertigo |103|1958-11-14|Action | 02:08
|
||||
</computeroutput>
|
||||
|
||||
-- close the cursor and commit work:
|
||||
--
|
||||
@@ -321,11 +342,6 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
<title>
|
||||
Compatibility
|
||||
</title>
|
||||
<para>
|
||||
The non-embedded use of cursors is a <productname>Postgres</productname>
|
||||
extension. The syntax and usage of cursors is being compared
|
||||
against the embedded form of cursors defined in <acronym>SQL92</acronym>.
|
||||
</para>
|
||||
|
||||
<refsect2 id="R2-SQL-FETCH-4">
|
||||
<refsect2info>
|
||||
@@ -334,6 +350,17 @@ FETCH RELATIVE 0 FROM <replaceable class="PARAMETER">cursor</replaceable>
|
||||
<title>
|
||||
SQL92
|
||||
</title>
|
||||
|
||||
<para>
|
||||
<note>
|
||||
<para>
|
||||
The non-embedded use of cursors is a <productname>Postgres</productname>
|
||||
extension. The syntax and usage of cursors is being compared
|
||||
against the embedded form of cursors defined in <acronym>SQL92</acronym>.
|
||||
</para>
|
||||
</note>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<acronym>SQL92</acronym> allows absolute positioning of the cursor for
|
||||
FETCH, and allows placing the results into explicit variables.
|
||||
|
||||
Reference in New Issue
Block a user