php - 使用 PHP 和 SQL 进行分页

Question

我一直在尝试解决分页问题，​​但我不理解以下代码。

                $lstart = ($page * 6) -6;
                $lend = ($page * 6)-1;
                $limit = $lstart.','.$lend;

我得到的结果好坏参半。我应该每页有六篇文章，但它是不一致的。该代码包含在我从其他人那里继承的脚本中，我正在尝试修复它。有人可以向我解释这段代码吗？在查询中，LIMIT=$limit。

Answer 1

它应该是...

$lstart = ($page * 6) -6; // quite frankly, it's clearer to write...
       // ($page - 1) * 6
$limit = $lstart.',6';

limit 中的第二个子句声明了多少项。没有达到某个点。

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来自 mysql 文档：（复制/粘贴）

SELECT * FROM tbl LIMIT 5,10;  # Retrieve rows 6-15

因此，1,10 将是第 2-11 行因此，要获得第 1 行，您需要将偏移量设置为零：0,10 这将为您提供第 1-10 行。

您还可以在此处查看有关 LIMIT 的更多教程：http: //php.about.com/od/mysqlcommands/g/Limit_sql.htm

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带解释的代码。

$rows_per_page = 6; // you're trying to get 6 rows for every "page".

// On page 1, you'd want rows 0-5 (6 rows inclusively)
// On page 2, you'd want rows 6-111 (again, 6 rows inclusively)
// and so forth.
// So when $page == 1, you want to start at 0, on page 2, start at 6....
// To express this pattern mathematically, we write:
$start = ($page - 1) * 6

// mysql takes offset and number as it's two variables in the LIMIT clause, 
// in that order, when two are provided.
// So we write:
$query = "SELECT * FROM table WHERE 1 LIMIT $start, $rows_per_page;";

// So, at page 1, you get
$query = "SELECT * FROM table WHERE 1 LIMIT 0, 6;"; // if we were to substitute the variables.
$query = "SELECT * FROM table WHERE 1 LIMIT 6, 6;"; // at page 2
$query = "SELECT * FROM table WHERE 1 LIMIT 12, 6;"; // at page 3