MySQL LIKE 运算符的行为类似于 = 运算符

Question

看起来 MySQL 的 LIKE 运算符的行为类似于 = 运算符。

以下 MySQL 查询返回预期结果(1 项):

$meta_key = '_locality';
$meta_value = 'The Hague';
$post_ids = $wpdb->get_col( $wpdb->prepare( 
  "
  SELECT      post_id
  FROM        $wpdb->postmeta
  WHERE       meta_key = %s
              AND meta_value LIKE %s
  ", 
  $meta_key, 
  $meta_value
) );

但是以下仅包含原始 meta_value 的一部分，返回一个空数组:

$meta_key = '_locality';
$meta_value = 'The';
$post_ids = $wpdb->get_col( $wpdb->prepare( 
  "
  SELECT      post_id
  FROM        $wpdb->postmeta
  WHERE       meta_key = %s
              AND meta_value LIKE %s
  ", 
  $meta_key, 
  $meta_value
) );

我在这里做错了什么？

Answer 1

请仔细阅读mysql模式匹配语法:http://dev.mysql.com/doc/refman/5.0/en/pattern-matching.html 。您因 LIKE 匹配而丢失 '%':

$meta_key = '_locality';
$meta_value = '%The Hague%';
$post_ids = $wpdb->get_col( $wpdb->prepare( 
  "
  SELECT      post_id
  FROM        $wpdb->postmeta
  WHERE       meta_key = %s
              AND meta_value LIKE %s
  ", 
  $meta_key, 
  $meta_value
) );