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<!-- doc/src/sgml/ref/create_foreign_table.sgml -->
<refentry id="SQL-CREATEFOREIGNTABLE">
<indexterm zone="sql-createforeigntable">
<primary>CREATE FOREIGN TABLE</primary>
</indexterm>
<refmeta>
<refentrytitle>CREATE FOREIGN TABLE</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>CREATE FOREIGN TABLE</refname>
<refpurpose>define a new foreign table</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable> ( [
<replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ] [ COLLATE <replaceable>collation</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
[, ... ]
] )
SERVER <replaceable class="parameter">server_name</replaceable>
[ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ]
<phrase>where <replaceable class="PARAMETER">column_constraint</replaceable> is:</phrase>
[ CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ]
{ NOT NULL |
NULL |
DEFAULT <replaceable>default_expr</replaceable> }
</synopsis>
</refsynopsisdiv>
<refsect1 id="SQL-CREATEFOREIGNTABLE-description">
<title>Description</title>
<para>
<command>CREATE FOREIGN TABLE</command> creates a new foreign table
in the current database. The table will be owned by the user issuing the
command.
</para>
<para>
If a schema name is given (for example, <literal>CREATE FOREIGN TABLE
myschema.mytable ...</>) then the table is created in the specified
schema. Otherwise it is created in the current schema.
The name of the foreign table must be
distinct from the name of any other foreign table, table, sequence, index,
view, or materialized view in the same schema.
</para>
<para>
<command>CREATE FOREIGN TABLE</command> also automatically creates a data
type that represents the composite type corresponding to one row of
the foreign table. Therefore, foreign tables cannot have the same
name as any existing data type in the same schema.
</para>
<para>
To be able to create a foreign table, you must have <literal>USAGE</literal>
privilege on the foreign server, as well as <literal>USAGE</literal>
privilege on all column types used in the table.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><literal>IF NOT EXISTS</></term>
<listitem>
<para>
Do not throw an error if a relation with the same name already exists.
A notice is issued in this case. Note that there is no guarantee that
the existing relation is anything like the one that would have been
created.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">table_name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of the table to be created.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">column_name</replaceable></term>
<listitem>
<para>
The name of a column to be created in the new table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">data_type</replaceable></term>
<listitem>
<para>
The data type of the column. This can include array
specifiers. For more information on the data types supported by
<productname>PostgreSQL</productname>, refer to <xref
linkend="datatype">.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>NOT NULL</></term>
<listitem>
<para>
The column is not allowed to contain null values.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>NULL</></term>
<listitem>
<para>
The column is allowed to contain null values. This is the default.
</para>
<para>
This clause is only provided for compatibility with
non-standard SQL databases. Its use is discouraged in new
applications.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DEFAULT
<replaceable>default_expr</replaceable></literal></term>
<listitem>
<para>
The <literal>DEFAULT</> clause assigns a default data value for
the column whose column definition it appears within. The value
is any variable-free expression (subqueries and cross-references
to other columns in the current table are not allowed). The
data type of the default expression must match the data type of the
column.
</para>
<para>
The default expression will be used in any insert operation that
does not specify a value for the column. If there is no default
for a column, then the default is null.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">server_name</replaceable></term>
<listitem>
<para>
The name of an existing foreign server to use for the foreign table.
For details on defining a server, see <xref
linkend="SQL-CREATESERVER">.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ...] )</literal></term>
<listitem>
<para>
Options to be associated with the new foreign table or one of its
columns.
The allowed option names and values are specific to each foreign
data wrapper and are validated using the foreign-data wrapper's
validator function. Duplicate option names are not allowed (although
it's OK for a table option and a column option to have the same name).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="SQL-CREATEFOREIGNTABLE-examples">
<title>Examples</title>
<para>
Create foreign table <structname>films</>, which will be accessed through
the server <structname>film_server</>:
<programlisting>
CREATE FOREIGN TABLE films (
code char(5) NOT NULL,
title varchar(40) NOT NULL,
did integer NOT NULL,
date_prod date,
kind varchar(10),
len interval hour to minute
)
SERVER film_server;
</programlisting></para>
</refsect1>
<refsect1 id="SQL-CREATEFOREIGNTABLE-compatibility">
<title id="SQL-CREATEFOREIGNTABLE-compatibility-title">Compatibility</title>
<para>
The <command>CREATE FOREIGN TABLE</command> command largely conforms to the
<acronym>SQL</acronym> standard; however, much as with
<link linkend="sql-createtable"><command>CREATE TABLE</></link>,
<literal>NULL</> constraints and zero-column foreign tables are permitted.
The ability to specify a default value is also a <productname>PostgreSQL</>
extension.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-alterforeigntable"></member>
<member><xref linkend="sql-dropforeigntable"></member>
<member><xref linkend="sql-createtable"></member>
<member><xref linkend="sql-createserver"></member>
</simplelist>
</refsect1>
</refentry>
|
