alter_table.sgml

PostgreSQL7.4.6 for Linux

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$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.62 2003/09/22 00:16:57 petere Exp $
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<refentry id="SQL-ALTERTABLE">
 <refmeta>
  <refentrytitle id="sql-altertable-title">ALTER TABLE</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>ALTER TABLE</refname>
  <refpurpose>change the definition of a table</refpurpose>
 </refnamediv>

 <indexterm zone="sql-altertable">
  <primary>ALTER TABLE</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ADD [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> <replaceable class="PARAMETER">type</replaceable> [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    DROP [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> [ RESTRICT | CASCADE ]
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET DEFAULT <replaceable class="PARAMETER">expression</replaceable> | DROP DEFAULT }
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET | DROP } NOT NULL
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STATISTICS <replaceable class="PARAMETER">integer</replaceable>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    SET WITHOUT OIDS
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    RENAME [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> TO <replaceable
    class="PARAMETER">new_column</replaceable>
ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
    RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    ADD <replaceable class="PARAMETER">table_constraint</replaceable>
ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
    DROP CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> [ RESTRICT | CASCADE ]
ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
    OWNER TO <replaceable class="PARAMETER">new_owner</replaceable>
ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
    CLUSTER ON <replaceable class="PARAMETER">index_name</replaceable>
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>ALTER TABLE</command> changes the definition of an existing table.
   There are several subforms:

  <variablelist>
   <varlistentry>
    <term><literal>ADD COLUMN</literal></term>
    <listitem>
     <para>
      This form adds a new column to the table using the same syntax as
      <xref linkend="SQL-CREATETABLE" endterm="SQL-CREATETABLE-TITLE">.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>DROP COLUMN</literal></term>
    <listitem>
     <para>
      This form drops a column from a table.  Indexes and
      table constraints involving the column will be automatically
      dropped as well.  You will need to say <literal>CASCADE</> if
      anything outside the table depends on the column, for example,
      foreign key references or views.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET</literal>/<literal>DROP DEFAULT</literal></term>
    <listitem>
     <para>
      These forms set or remove the default value for a column.
      The default values only apply to subsequent <command>INSERT</command>
      commands; they do not cause rows already in the table to change.
      Defaults may also be created for views, in which case they are
      inserted into <command>INSERT</> statements on the view before
      the view's <literal>ON INSERT</literal> rule is applied.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET</literal>/<literal>DROP NOT NULL</literal></term>
    <listitem>
     <para>
      These forms change whether a column is marked to allow null
      values or to reject null values.  You can only use <literal>SET
      NOT NULL</> when the column contains no null values.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET STATISTICS</literal></term>
    <listitem>
     <para>
      This form
      sets the per-column statistics-gathering target for subsequent
      <xref linkend="sql-analyze" endterm="sql-analyze-title"> operations.
      The target can be set in the range 0 to 1000; alternatively, set it
      to -1 to revert to using the system default statistics target.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET STORAGE</literal></term>
    <listitem>
     <para>
      This form sets the storage mode for a column. This controls whether this
      column is held inline or in a supplementary table, and whether the data
      should be compressed or not. <literal>PLAIN</literal> must be used
      for fixed-length values such as <type>integer</type> and is
      inline, uncompressed. <literal>MAIN</literal> is for inline,
      compressible data. <literal>EXTERNAL</literal> is for external,
      uncompressed data, and <literal>EXTENDED</literal> is for external,
      compressed data.  <literal>EXTENDED</literal> is the default for all
      data types that support it.  The use of <literal>EXTERNAL</literal> will, for example,
      make substring operations on a <type>text</type> column faster, at the penalty of
      increased storage space.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>SET WITHOUT OIDS</literal></term>
    <listitem>
     <para>
      This form removes the <literal>oid</literal> column from the
      table.  Removing OIDs from a table does not occur immediately.
      The space that the OID uses will be reclaimed when the row is
      updated.  Without updating the row, both the space and the value
      of the OID are kept indefinitely.  This is semantically similar
      to the <literal>DROP COLUMN</literal> process.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RENAME</literal></term>
    <listitem>
     <para>
      The <literal>RENAME</literal> forms change the name of a table
      (or an index, sequence, or view) or the name of an individual column in
      a table. There is no effect on the stored data.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>ADD <replaceable class="PARAMETER">table_constraint</replaceable></literal></term>
    <listitem>
     <para>
      This form adds a new constraint to a table using the same syntax as
      <xref linkend="SQL-CREATETABLE" endterm="SQL-CREATETABLE-TITLE">. 
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>DROP CONSTRAINT</literal></term>
    <listitem>
     <para>
      This form drops constraints on a table.
      Currently, constraints on tables are not required to have unique
      names, so there may be more than one constraint matching the specified
      name.  All such constraints will be dropped.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>OWNER</literal></term>
    <listitem>
     <para>
      This form changes the owner of the table, index, sequence, or view to the
      specified user.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CLUSTER</literal></term>
    <listitem>
     <para>
      This form marks a table for future <xref linkend="SQL-CLUSTER" endterm="sql-cluster-title">
      operations.
     </para>
    </listitem>
   </varlistentry>

  </variablelist>
  </para>

  <para>
   You must own the table to use <command>ALTER TABLE</>; except for
   <command>ALTER TABLE OWNER</>, which may only be executed by a superuser.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

    <variablelist>

     <varlistentry>
      <term><replaceable class="PARAMETER">name</replaceable></term>
      <listitem>
       <para>
	The name (possibly schema-qualified) of an existing table to
	alter. If <literal>ONLY</> is specified, only that table is
	altered. If <literal>ONLY</> is not specified, the table and all
	its descendant tables (if any) are updated. <literal>*</> can be
	appended to the table name to indicate that descendant tables are
	to be altered, but in the current version, this is the default
	behavior.  (In releases before 7.1, <literal>ONLY</> was the
	default behavior.  The default can be altered by changing the
	configuration parameter <varname>sql_inheritance</varname>.)
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="PARAMETER">column</replaceable></term>
      <listitem>
       <para>
	Name of a new or existing column.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="PARAMETER">type</replaceable></term>
      <listitem>
       <para>
	Data type of the new column.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><replaceable class="PARAMETER">new_column</replaceable></term>
      <listitem>