copy.sgml

postgresql8.3.4源码,开源数据库

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<refentry id="SQL-COPY">
 <refmeta>
  <refentrytitle id="sql-copy-title">COPY</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>COPY</refname>
  <refpurpose>copy data between a file and a table</refpurpose>
 </refnamediv>

 <indexterm zone="sql-copy">
  <primary>COPY</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
    FROM { '<replaceable class="parameter">filename</replaceable>' | STDIN }
    [ [ WITH ] 
          [ BINARY ]
          [ OIDS ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null string</replaceable>' ]
          [ CSV [ HEADER ]
                [ QUOTE [ AS ] '<replaceable class="parameter">quote</replaceable>' ] 
                [ ESCAPE [ AS ] '<replaceable class="parameter">escape</replaceable>' ]
                [ FORCE NOT NULL <replaceable class="parameter">column</replaceable> [, ...] ]

COPY { <replaceable class="parameter">tablename</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ] | ( <replaceable class="parameter">query</replaceable> ) }
    TO { '<replaceable class="parameter">filename</replaceable>' | STDOUT }
    [ [ WITH ] 
          [ BINARY ]
          [ HEADER ]
          [ OIDS ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null string</replaceable>' ]
          [ CSV [ HEADER ]
                [ QUOTE [ AS ] '<replaceable class="parameter">quote</replaceable>' ] 
                [ ESCAPE [ AS ] '<replaceable class="parameter">escape</replaceable>' ]
                [ FORCE QUOTE <replaceable class="parameter">column</replaceable> [, ...] ]
</synopsis>
 </refsynopsisdiv>
 
 <refsect1>
  <title>Description</title>

  <para>
   <command>COPY</command> moves data between
   <productname>PostgreSQL</productname> tables and standard file-system
   files. <command>COPY TO</command> copies the contents of a table
   <emphasis>to</> a file, while <command>COPY FROM</command> copies
   data <emphasis>from</> a file to a table (appending the data to
   whatever is in the table already).  <command>COPY TO</command>
   can also copy the results of a <command>SELECT</> query.
  </para>

  <para>
   If a list of columns is specified, <command>COPY</command> will
   only copy the data in the specified columns to or from the file.
   If there are any columns in the table that are not in the column list,
   <command>COPY FROM</command> will insert the default values for
   those columns.
  </para>

  <para>
   <command>COPY</command> with a file name instructs the
   <productname>PostgreSQL</productname> server to directly read from
   or write to a file. The file must be accessible to the server and
   the name must be specified from the viewpoint of the server. When
   <literal>STDIN</literal> or <literal>STDOUT</literal> is
   specified, data is transmitted via the connection between the
   client and the server.
  </para>
 </refsect1>
  
 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">tablename</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing table.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">column</replaceable></term>
     <listitem>
     <para>
      An optional list of columns to be copied.  If no column list is
      specified, all columns of the table will be copied.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">query</replaceable></term>
    <listitem>
     <para>
      A <xref linkend="sql-select" endterm="sql-select-title"> or
      <xref linkend="sql-values" endterm="sql-values-title"> command
      whose results are to be copied.
      Note that parentheses are required around the query.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">filename</replaceable></term>
    <listitem>
     <para>
      The absolute path name of the input or output file.  Windows users
      might need to use an <literal>E''</> string and double backslashes
      used as path separators.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>STDIN</literal></term>
    <listitem>
     <para>
      Specifies that input comes from the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>STDOUT</literal></term>
    <listitem>
     <para>
      Specifies that output goes to the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>BINARY</literal></term>
    <listitem>
     <para>
      Causes all data to be stored or read in binary format rather
      than as text. You cannot specify the <option>DELIMITER</option>,
      <option>NULL</option>, or <option>CSV</> options in binary mode.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>OIDS</literal></term>
    <listitem>
     <para>
      Specifies copying the OID for each row.  (An error is raised if
      <literal>OIDS</literal> is specified for a table that does not
      have OIDs, or in the case of copying a <replaceable
      class="parameter">query</replaceable>.)
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">delimiter</replaceable></term>
    <listitem>
     <para>
      The single ASCII character that separates columns within each row
      (line) of the file.  The default is a tab character in text mode,
      a comma in <literal>CSV</> mode.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">null string</replaceable></term>
    <listitem>
     <para>
      The string that represents a null value. The default is
      <literal>\N</literal> (backslash-N) in text mode, and a empty
      value with no quotes in <literal>CSV</> mode. You might prefer an
      empty string even in text mode for cases where you don't want to
      distinguish nulls from empty strings.
     </para>

     <note>
      <para>
       When using <command>COPY FROM</command>, any data item that matches
       this string will be stored as a null value, so you should make
       sure that you use the same string as you used with
       <command>COPY TO</command>.
      </para>
     </note>

    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CSV</literal></term>
    <listitem>
     <para>
      Selects Comma Separated Value (<literal>CSV</>) mode.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>HEADER</literal></term>
    <listitem>
     <para>
      Specifies the file contains a header line with the names of each
      column in the file.  On output, the first line contains the column 
      names from the table, and on input, the first line is ignored.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">quote</replaceable></term>
    <listitem>
     <para>
      Specifies the ASCII quotation character in <literal>CSV</> mode.
      The default is double-quote.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">escape</replaceable></term>
    <listitem>
     <para>
      Specifies the ASCII character that should appear before a
      <literal>QUOTE</> data character value in <literal>CSV</> mode.
      The default is the <literal>QUOTE</> value (usually double-quote).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>FORCE QUOTE</></term>
    <listitem>
     <para>
      In <literal>CSV</> <command>COPY TO</> mode, forces quoting to be
      used for all non-<literal>NULL</> values in each specified column.
      <literal>NULL</> output is never quoted.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>FORCE NOT NULL</></term>
    <listitem>
     <para>
      In <literal>CSV</> <command>COPY FROM</> mode, process each
      specified column as though it were quoted and hence not a
      <literal>NULL</> value. For the default null string in
      <literal>CSV</> mode (<literal>''</>), this causes missing
      values to be input as zero-length strings.
     </para>
    </listitem>
   </varlistentry>

  </variablelist>
 </refsect1>

 <refsect1>
  <title>Outputs</title>

  <para>
   On successful completion, a <command>COPY</> command returns a command
   tag of the form
<screen>
COPY <replaceable class="parameter">count</replaceable>
</screen>
   The <replaceable class="parameter">count</replaceable> is the number
   of rows copied.
  </para>
 </refsect1>

 <refsect1>
  <title>Notes</title>

   <para>
    <command>COPY</command> can only be used with plain tables, not
    with views.  However, you can write <literal>COPY (SELECT * FROM
    <replaceable class="parameter">viewname</replaceable>) TO ...</literal>.
   </para>

   <para>
    The <literal>BINARY</literal> key word causes all data to be
    stored/read as binary format rather than as text.  It is
    somewhat faster than the normal text mode, but a binary-format
    file is less portable across machine architectures and
    <productname>PostgreSQL</productname> versions.
   </para>

   <para>
    You must have select privilege on the table
    whose values are read by <command>COPY TO</command>, and
    insert privilege on the table into which values
    are inserted by <command>COPY FROM</command>.
   </para>

   <para>
    Files named in a <command>COPY</command> command are read or written
    directly by the server, not by the client application. Therefore,
    they must reside on or be accessible to the database server machine,
    not the client. They must be accessible to and readable or writable
    by the <productname>PostgreSQL</productname> user (the user ID the
    server runs as), not the client. <command>COPY</command> naming a
    file is only allowed to database superusers, since it allows reading
    or writing any file that the server has privileges to access.
   </para>

   <para>
    Do not confuse <command>COPY</command> with the
    <application>psql</application> instruction
    <command>\copy</command>. <command>\copy</command> invokes
    <command>COPY FROM STDIN</command> or <command>COPY TO
    STDOUT</command>, and then fetches/stores the data in a file
    accessible to the <application>psql</application> client. Thus,
    file accessibility and access rights depend on the client rather
    than the server when <command>\copy</command> is used.
   </para>

   <para>
    It is recommended that the file name used in <command>COPY</command>
    always be specified as an absolute path. This is enforced by the
    server in the case of <command>COPY TO</command>, but for
    <command>COPY FROM</command> you do have the option of reading from
    a file specified by a relative path. The path will be interpreted
    relative to the working directory of the server process (normally
    the cluster's data directory), not the client's working directory.
   </para>

   <para>
    <command>COPY FROM</command> will invoke any triggers and check
    constraints on the destination table. However, it will not invoke rules.
   </para>

   <para>
    <command>COPY</command> input and output is affected by
    <varname>DateStyle</varname>. To ensure portability to other
    <productname>PostgreSQL</productname> installations that might use
    non-default <varname>DateStyle</varname> settings,
    <varname>DateStyle</varname> should be set to <literal>ISO</> before
    using <command>COPY TO</>.
   </para>

   <para>
    Input data is interpreted according to the current client encoding,
    and output data is encoded in the the current client encoding, even
    if the data does not pass through the client but is read from or
    written to a file.
   </para>

   <para>
    <command>COPY</command> stops operation at the first error. This
    should not lead to problems in the event of a <command>COPY
    TO</command>, but the target table will already have received
    earlier rows in a <command>COPY FROM</command>. These rows will not
    be visible or accessible, but they still occupy disk space. This might
    amount to a considerable amount of wasted disk space if the failure
    happened well into a large copy operation. You might wish to invoke
    <command>VACUUM</command> to recover the wasted space.
   </para>

 </refsect1>
 
 <refsect1>
  <title>File Formats</title>

  <refsect2>
   <title>Text Format</title>

   <para>
    When <command>COPY</command> is used without the <literal>BINARY</literal>
    or <literal>CSV</> options,
    the data read or written is a text file with one line per table row.
    Columns in a row are separated by the delimiter character.
    The column values themselves are strings generated by the
    output function, or acceptable to the input function, of each
    attribute's data type.  The specified null string is used in
    place of columns that are null.
    <command>COPY FROM</command> will raise an error if any line of the
    input file contains more or fewer columns than are expected.
    If <literal>OIDS</literal> is specified, the OID is read or written as the first column,
    preceding the user data columns.
   </para>

   <para>
    End of data can be represented by a single line containing just
    backslash-period (<literal>\.</>).  An end-of-data marker is
    not necessary when reading from a file, since the end of file
    serves perfectly well; it is needed only when copying data to or from
    client applications using pre-3.0 client protocol.
   </para>

   <para>
    Backslash characters (<literal>\</>) can be used in the
    <command>COPY</command> data to quote data characters that might
    otherwise be taken as row or column delimiters. In particular, the
    following characters <emphasis>must</> be preceded by a backslash if
    they appear as part of a column value: backslash itself,
    newline, carriage return, and the current delimiter character.
   </para>

   <para>