php - 选择第 n 页而不是第 n 页

Question

我有一个网页，它对我的​​ MySQL 数据库的结果进行分页。下面的代码用于创建下拉菜单来导航结果。目前它被设置为选择页面n；这假设当我请求第 30 页(例如)时，相关记录存储在结果集的第 30 行，但从一些测试来看，情况显然并非如此。我应该如何更改它，以便它返回第 n 页？我知道 while 语句需要调整，但我就是不太明白。

    //…previous code…

    $rowsPerPage = 1;

    // by default we show first page
    $pageNum = 1;

    // if $_GET['page'] defined, use it as page number
    if(isset($_GET['page']))
    {
        $pageNum = $_GET['page'];
    }

    $offset = ($pageNum - 1) * $rowsPerPage;

    $query3 = 'SELECT t1.s_name AS t1_sname, t1.uh_heading AS t1_unit, t1.ut_latin AS t1_latin, t1.ut_english AS t1_english, t1.uh_id, t1.chapter_sequence AS t1_chapters, t1.unit_sequence AS t1_units, 
                      t2.s_name AS t2_sname, t2.ut_latin AS t2_latin, t2.ut_english AS t2_english, t2.chapter_sequence AS t2_chapters, t2.unit_sequence AS t2_units
               FROM vw_source_text_and_translation AS t1
               LEFT JOIN vw_source_text_and_translation AS t2
               ON (t2.uh_id = t1.uh_id AND t2.s_id = " ' . $_SESSION['source2'] . ' " )
               WHERE t1.s_id =  " ' . $_SESSION['source1'] . ' "
               ORDER BY t1.chapter_sequence, t1.unit_sequence' .
               " LIMIT $offset, $rowsPerPage";

//...more code...

    $query4   = 'SELECT uh_id, chapter_sequence, unit_sequence, uh_heading 
             FROM vw_source_text_and_translation 
             WHERE s_id = "' . $_SESSION['source1'] . '"';

//...more code...

    $rows= $result4;
    $numrows = 0;
    $nav  = '';
    while ($row = mysql_fetch_assoc($rows)) 
    {
      $nav .= ' <option value="'. $row['uh_id'] .'"> '. 
              $row['chapter_sequence'] .'.'.$row['unit_sequence'] .
              ' - '. $row['uh_heading'] .'</option>';
      $numrows ++;
    }

    /*…more code… */

好的，在一些帮助下，这个问题已部分修复； while 语句现在读作:

while ($row = mysql_fetch_assoc($rows)) 
 {
  $numrows ++;
  $nav .= ' <option value=" ' . $numrows . '"> '. $row['chapter_sequence'] .'.'.
             $row['unit_sequence'] .' - '. $row['uh_heading'] .'</option>';
 }

这修复了分页，尽管我仍然遇到一些记录未显示的问题，即使当我在 MySQL Toolkit 中运行 $query3 并设置 $_SESSION['source1'] 和 $_SESSION['source2'] 的值时也是如此效果很好。似乎如果 t2.ut_latin 或 t2.ut_english 为 NULL 值，则不会显示任何数据，即使它识别出存在一条已分页的记录。但是，我想这超出了这个问题的主题，所以我可能不得不在新问题中重新发布这个问题。

Answer 1

您应该使用带有偏移量的 LIMIT 子句。

SELECT col1, col2, col3
FROM yourtable
ORDER BY something
LIMIT 40, 10

要计算偏移量，请将页码(从 0 开始)乘以每页的行数。