mysql-fetch-field.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.mysql-fetch-field" xmlns="http://docbook.org/ns/docbook">
   <refnamediv>
    <refname>mysql_fetch_field</refname>
    <refpurpose>
     从结果集中取得列信息并作为对象返回
    </refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <warning>
   &mysql.alternative.note;
   <simplelist role="alternatives">
    <member><function>mysqli_fetch_field</function></member>
    <member><methodname>PDOStatement::getColumnMeta</methodname></member>
   </simplelist>
  </warning>
 </refsynopsisdiv>

 <refsect1 role="description">
  &reftitle.description;
     <methodsynopsis>
      <type>object</type><methodname>mysql_fetch_field</methodname>
      <methodparam><type>resource</type><parameter>result</parameter></methodparam>
      <methodparam choice="opt"><type>int</type><parameter>field_offset</parameter></methodparam>
     </methodsynopsis>
    <para>
     返回一个包含字段信息的对象。
    </para>
    <para>
     <function>mysql_fetch_field</function>
     可以用来从某个查询结果中取得字段的信息。如果没有指定字段偏移量，则下一个尚未被
     <function>mysql_fetch_field</function> 取得的字段被提取。
    </para>
    <para>
     对象的属性为：
     <itemizedlist>
      <listitem>
       <simpara>
        name - 列名
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        table - 该列所在的表名，which is the alias name if one is defined
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        max_length - 该列最大长度
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        not_null - 1，如果该列不能为 &null;
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        primary_key - 1，如果该列是 primary key
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        unique_key - 1，如果该列是 unique key
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        multiple_key - 1，如果该列是 non-unique key
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        numeric - 1，如果该列是 numeric
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        blob - 1，如果该列是 BLOB
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        type - 该列的类型
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        unsigned - 1，如果该列是无符号数
       </simpara>
      </listitem>
      <listitem>
       <simpara>
        zerofill - 1，如果该列是 zero-filled
       </simpara>
      </listitem>
     </itemizedlist>
    </para>
    &database.field-case;
    <para>
     <example>
      <title><function>mysql_fetch_field</function></title>
      <programlisting role="php">
<![CDATA[
<?php
mysql_connect('localhost:3306', $user, $password)
    or die("Could not connect: " . mysql_error());
mysql_select_db("database");
$result = mysql_query("select * from table")
    or die("Query failed: " . mysql_error());
/* get column metadata */
$i = 0;
while ($i < mysql_num_fields($result)) {
    echo "Information for column $i:<br />\n";
    $meta = mysql_fetch_field($result);
    if (!$meta) {
        echo "No information available<br />\n";
    }
    echo "<pre>
blob:         $meta->blob
max_length:   $meta->max_length
multiple_key: $meta->multiple_key
name:         $meta->name
not_null:     $meta->not_null
numeric:      $meta->numeric
primary_key:  $meta->primary_key
table:        $meta->table
type:         $meta->type
unique_key:   $meta->unique_key
unsigned:     $meta->unsigned
zerofill:     $meta->zerofill
</pre>";
    $i++;
}
mysql_free_result($result);
?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     参见 <function>mysql_field_seek</function>。
    </para>
   </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    &mysql.result.description;
    <varlistentry>
     <term><parameter>field_offset</parameter></term>
     <listitem>
      <para>
       The numerical field offset. If the field offset is not specified, the 
       next field that was not yet retrieved by this function is retrieved. 
       The <parameter>field_offset</parameter> starts at <literal>0</literal>.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns an <type>object</type> containing field information. The properties 
   of the object are:
  </para>
  <para>
   <itemizedlist>
    <listitem>
     <simpara>
      name - column name
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      table - name of the table the column belongs to
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      max_length - maximum length of the column
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      not_null - 1 if the column cannot be &null;
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      primary_key - 1 if the column is a primary key
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      unique_key - 1 if the column is a unique key
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      multiple_key - 1 if the column is a non-unique key
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      numeric - 1 if the column is numeric
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      blob - 1 if the column is a BLOB
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      type - the type of the column
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      unsigned - 1 if the column is unsigned
     </simpara>
    </listitem>
    <listitem>
     <simpara>
      zerofill - 1 if the column is zero-filled
     </simpara>
    </listitem>
   </itemizedlist>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>mysql_fetch_field</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$conn = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$conn) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db('database');
$result = mysql_query('select * from table');
if (!$result) {
    die('Query failed: ' . mysql_error());
}
/* get column metadata */
$i = 0;
while ($i < mysql_num_fields($result)) {
    echo "Information for column $i:<br />\n";
    $meta = mysql_fetch_field($result, $i);
    if (!$meta) {
        echo "No information available<br />\n";
    }
    echo "<pre>
blob:         $meta->blob
max_length:   $meta->max_length
multiple_key: $meta->multiple_key
name:         $meta->name
not_null:     $meta->not_null
numeric:      $meta->numeric
primary_key:  $meta->primary_key
table:        $meta->table
type:         $meta->type
unique_key:   $meta->unique_key
unsigned:     $meta->unsigned
zerofill:     $meta->zerofill
</pre>";
    $i++;
}
mysql_free_result($result);
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &database.field-case;
  <note>
   <para>
    If field or tablenames are aliased in the SQL query the aliased name will
    be returned. The original name can be retrieved for instance by using
    <methodname>mysqli_result::fetch_field</methodname>.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>mysql_field_seek</function></member>
   </simplelist>
  </para>
 </refsect1>
  </refentry>

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