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176 lines
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176 lines
6.3 KiB
Plaintext
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/comment.sgml,v 1.23 2003/09/09 18:28:52 tgl Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-COMMENT">
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<refmeta>
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<refentrytitle id="SQL-COMMENT-TITLE">COMMENT</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>COMMENT</refname>
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<refpurpose>define or change the comment of an object</refpurpose>
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</refnamediv>
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<indexterm zone="sql-comment">
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<primary>COMMENT</primary>
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</indexterm>
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<refsynopsisdiv>
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<synopsis>
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COMMENT ON
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{
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TABLE <replaceable class="PARAMETER">object_name</replaceable> |
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COLUMN <replaceable class="PARAMETER">table_name</replaceable>.<replaceable class="PARAMETER">column_name</replaceable> |
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AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable class="PARAMETER">agg_type</replaceable>) |
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CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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DATABASE <replaceable class="PARAMETER">object_name</replaceable> |
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DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
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FUNCTION <replaceable class="PARAMETER">func_name</replaceable> (<replaceable class="PARAMETER">arg1_type</replaceable>, <replaceable class="PARAMETER">arg2_type</replaceable>, ...) |
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INDEX <replaceable class="PARAMETER">object_name</replaceable> |
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OPERATOR <replaceable class="PARAMETER">op</replaceable> (<replaceable class="PARAMETER">leftoperand_type</replaceable>, <replaceable class="PARAMETER">rightoperand_type</replaceable>) |
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RULE <replaceable class="PARAMETER">rule_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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SCHEMA <replaceable class="PARAMETER">object_name</replaceable> |
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SEQUENCE <replaceable class="PARAMETER">object_name</replaceable> |
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TRIGGER <replaceable class="PARAMETER">trigger_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
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TYPE <replaceable class="PARAMETER">object_name</replaceable> |
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VIEW <replaceable class="PARAMETER">object_name</replaceable>
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} IS <replaceable class="PARAMETER">'text'</replaceable>
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>COMMENT</command> stores a comment about a database object.
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Comments can be
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easily retrieved with the <application>psql</application> commands
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<command>\dd</command>, <command>\d+</command>, and <command>\l+</command>.
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Other user interfaces to retrieve comments can be built atop
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the same built-in functions that <application>psql</application> uses, namely
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<function>obj_description</> and <function>col_description</>.
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</para>
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<para>
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To modify a comment, issue a new <command>COMMENT</> command for the
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same object. Only one comment string is stored for each object.
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To remove a comment, write <literal>NULL</literal> in place of the text
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string.
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Comments are automatically dropped when the object is dropped.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><replaceable class="parameter">object_name</replaceable></term>
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<term><replaceable class="parameter">table_name.column_name</replaceable></term>
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<term><replaceable class="parameter">aggname</replaceable></term>
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<term><replaceable class="parameter">constraint_name</replaceable></term>
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<term><replaceable class="parameter">func_name</replaceable></term>
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<term><replaceable class="parameter">op</replaceable></term>
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<term><replaceable class="parameter">rule_name</replaceable></term>
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<term><replaceable class="parameter">trigger_name</replaceable></term>
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<listitem>
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<para>
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The name of the object to be be commented. Names of tables,
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aggregates, domains, functions, indexes, operators, sequences,
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types, and views may be schema-qualified.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">text</replaceable></term>
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<listitem>
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<para>
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The new comment.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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There is presently no security mechanism for comments: any user
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connected to a database can see all the comments for objects in
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that database (although only superusers can change comments for
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objects that they don't own). Therefore, don't put
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security-critical information in comments.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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Attach a comment to the table <literal>mytable</literal>:
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<programlisting>
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COMMENT ON TABLE mytable IS 'This is my table.';
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</programlisting>
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Remove it again:
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<programlisting>
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COMMENT ON TABLE mytable IS NULL;
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</programlisting>
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</para>
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<para>
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Some more examples:
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<programlisting>
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COMMENT ON AGGREGATE my_aggregate (double precision) IS 'Computes sample variance';
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COMMENT ON COLUMN my_table.my_column IS 'Employee ID number';
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COMMENT ON DATABASE my_database IS 'Development Database';
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COMMENT ON DOMAIN my_domain IS 'Email Address Domain';
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COMMENT ON FUNCTION my_function (timestamp) IS 'Returns Roman Numeral';
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COMMENT ON INDEX my_index IS 'Enforces uniqueness on employee ID';
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COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts';
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COMMENT ON OPERATOR ^ (NONE, text) IS 'This is a prefix operator on text';
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COMMENT ON RULE my_rule ON my_table IS 'Logs updates of employee records';
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COMMENT ON SCHEMA my_schema IS 'Departmental data';
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COMMENT ON SEQUENCE my_sequence IS 'Used to generate primary keys';
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COMMENT ON TABLE my_schema.my_table IS 'Employee Information';
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COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI';
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COMMENT ON TYPE complex IS 'Complex number data type';
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COMMENT ON VIEW my_view IS 'View of departmental costs';
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</programlisting>
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</para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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There is no <command>COMMENT</command> command in the SQL standard.
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"../reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:"/usr/lib/sgml/catalog"
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sgml-local-ecat-files:nil
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End:
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-->
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