$wpdb->prepare() 支持sprintf() arguments. 这个%d 是整数的占位符（不是十进制，应该是%f).

使用%d 如果要向数据库发送实整数，请使用%s 对于字符串。

例如：

$post_id  = \'2\';
$prepared = $wpdb->prepare(
    "SELECT * FROM $wpdb->posts WHERE post_id = %d", 
    $post_id 
);

这里我们使用%d 以确保查询整数。如果我们使用%s, 不会有严格的匹配，因为$post_id 是PHP代码段中的字符串。

$wpdb->prepare() 在不确定值的格式时非常有用。

那么，您如何知道每个字段所需的类型呢？您可以在中查找此信息wp-admin/includes/schema.php. 的示例posts 表格：

CREATE TABLE $wpdb->posts (
  ID bigint(20) unsigned NOT NULL auto_increment,
  post_author bigint(20) unsigned NOT NULL default \'0\',
  post_date datetime NOT NULL default \'0000-00-00 00:00:00\',
  post_date_gmt datetime NOT NULL default \'0000-00-00 00:00:00\',
  post_content longtext NOT NULL,
  post_title text NOT NULL,
  post_excerpt text NOT NULL,
  post_status varchar(20) NOT NULL default \'publish\',
  comment_status varchar(20) NOT NULL default \'open\',
  ping_status varchar(20) NOT NULL default \'open\',
  post_password varchar(20) NOT NULL default \'\',
  post_name varchar(200) NOT NULL default \'\',
  to_ping text NOT NULL,
  pinged text NOT NULL,
  post_modified datetime NOT NULL default \'0000-00-00 00:00:00\',
  post_modified_gmt datetime NOT NULL default \'0000-00-00 00:00:00\',
  post_content_filtered longtext NOT NULL,
  post_parent bigint(20) unsigned NOT NULL default \'0\',
  guid varchar(255) NOT NULL default \'\',
  menu_order int(11) NOT NULL default \'0\',
  post_type varchar(20) NOT NULL default \'post\',
  post_mime_type varchar(100) NOT NULL default \'\',
  comment_count bigint(20) NOT NULL default \'0\',
  PRIMARY KEY  (ID),
  KEY post_name (post_name),
  KEY type_status_date (post_type,post_status,post_date,ID),
  KEY post_parent (post_parent),
  KEY post_author (post_author)
) $charset_collate;\\n";

所有声明为bigint 或int 需要%d, 因为这些字段是整数。*text, varchar 和datetime 要求%s.

您还可以在PHP脚本中以编程方式查询该信息：

global $wpdb;

$table_data = $wpdb->get_results( "DESCRIBE $wpdb->posts" );
print \'<pre>\' . print_r( $table_data, 1 ) . \'</pre>\';

结果如下所示：

Array
(
    [0] => stdClass Object
        (
            [Field] => ID
            [Type] => bigint(20) unsigned
            [Null] => NO
            [Key] => PRI
            [Default] => 
            [Extra] => auto_increment
        )

    [1] => stdClass Object
        (
            [Field] => post_author
            [Type] => bigint(20) unsigned
            [Null] => NO
            [Key] => MUL
            [Default] => 0
            [Extra] => 
        )

    [2] => stdClass Object
        (
            [Field] => post_date
            [Type] => datetime
            [Null] => NO
            [Key] => 
            [Default] => 0000-00-00 00:00:00
            [Extra] => 
        )

    [3] => stdClass Object
        (
            [Field] => post_date_gmt
            [Type] => datetime
            [Null] => NO
            [Key] => 
            [Default] => 0000-00-00 00:00:00
            [Extra] => 
        )

    [4] => stdClass Object
        (
            [Field] => post_content
            [Type] => longtext
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [5] => stdClass Object
        (
            [Field] => post_title
            [Type] => text
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [6] => stdClass Object
        (
            [Field] => post_excerpt
            [Type] => text
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [7] => stdClass Object
        (
            [Field] => post_status
            [Type] => varchar(20)
            [Null] => NO
            [Key] => 
            [Default] => publish
            [Extra] => 
        )

    [8] => stdClass Object
        (
            [Field] => comment_status
            [Type] => varchar(20)
            [Null] => NO
            [Key] => 
            [Default] => open
            [Extra] => 
        )

    [9] => stdClass Object
        (
            [Field] => ping_status
            [Type] => varchar(20)
            [Null] => NO
            [Key] => 
            [Default] => open
            [Extra] => 
        )

    [10] => stdClass Object
        (
            [Field] => post_password
            [Type] => varchar(20)
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [11] => stdClass Object
        (
            [Field] => post_name
            [Type] => varchar(200)
            [Null] => NO
            [Key] => MUL
            [Default] => 
            [Extra] => 
        )

    [12] => stdClass Object
        (
            [Field] => to_ping
            [Type] => text
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [13] => stdClass Object
        (
            [Field] => pinged
            [Type] => text
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [14] => stdClass Object
        (
            [Field] => post_modified
            [Type] => datetime
            [Null] => NO
            [Key] => 
            [Default] => 0000-00-00 00:00:00
            [Extra] => 
        )

    [15] => stdClass Object
        (
            [Field] => post_modified_gmt
            [Type] => datetime
            [Null] => NO
            [Key] => 
            [Default] => 0000-00-00 00:00:00
            [Extra] => 
        )

    [16] => stdClass Object
        (
            [Field] => post_content_filtered
            [Type] => longtext
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [17] => stdClass Object
        (
            [Field] => post_parent
            [Type] => bigint(20) unsigned
            [Null] => NO
            [Key] => MUL
            [Default] => 0
            [Extra] => 
        )

    [18] => stdClass Object
        (
            [Field] => guid
            [Type] => varchar(255)
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [19] => stdClass Object
        (
            [Field] => menu_order
            [Type] => int(11)
            [Null] => NO
            [Key] => 
            [Default] => 0
            [Extra] => 
        )

    [20] => stdClass Object
        (
            [Field] => post_type
            [Type] => varchar(20)
            [Null] => NO
            [Key] => MUL
            [Default] => post
            [Extra] => 
        )

    [21] => stdClass Object
        (
            [Field] => post_mime_type
            [Type] => varchar(100)
            [Null] => NO
            [Key] => 
            [Default] => 
            [Extra] => 
        )

    [22] => stdClass Object
        (
            [Field] => comment_count
            [Type] => bigint(20)
            [Null] => NO
            [Key] => 
            [Default] => 0
            [Extra] => 
        )
)

您现在可以使用Type 输入以确定正确的占位符。对于核心表，我不会这样做，只需使用在schema.php. 来自第三方代码的自定义表是另一种情况，检查这些表有时可能有用。