如何在PHP中使用MySQL Found\u Rows()?

SQL_CALC_FOUND_ROWS LIMIT 但是仍然想知道如果没有 限制 .

想想这是怎么回事:

SELECT SQL_CALC_FOUND_ROWS * FROM Users;

您强制数据库检索/解析表中的所有数据,然后将其丢弃。即使您不打算检索任何行,DB服务器仍将开始从磁盘中提取实际数据,前提是您需要这些数据。

鉴于,做:

SELECT count(*) FROM users;

它的两个问题:

$query = 'SELECT SQL_CALC_FOUND_ROWS * FROM Users';
mysql_query($query);
$query = 'SELECT FOUND_ROWS()';
mysql_query($query);

一个常见的误解是,SQL\u CALC\u FOUND\u ROWS的性能比COUNT()好。看一下Percona的比较: http://www.mysqlperformanceblog.com/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/

回答您的问题:每个mysql\u查询调用只允许一个查询,如手册中所述: mysql_query() sends a unique query (multiple queries are not supported)

ext/mysqli 作为MySQL扩展:

http://www.php.net/manual/en/mysqli.multi-query.php

只有这个代码对我有效,所以我想和你分享。

$Result=mysqli_query($i_link,"SELECT SQL_CALC_FOUND_ROWS  id From users LIMIT 10"); 
$NORResult=mysqli_query($i_link,"Select FOUND_ROWS()"); 
$NORRow=mysqli_fetch_array($NORResult); 
$NOR=$NORRow["FOUND_ROWS()"]; 
echo $NOR;

$sql="(select sql_calc_found_rows tb.*, tb1.title
      from orders tb
           left join goods tb1 on tb.goods_id=tb1.id
      where {$where}
      order by created desc
      limit {$offset}, {$page_size})
      union
      (select found_rows(), '', '', '', '', '', '', '', '', '')
     ";
$rs=$db->query($sql)->result_array();
$total=array_pop($rs);
$total=$total['id'];

这是一个简单的方法&为我工作:

$query = "
SELECT SQL_CALC_FOUND_ROWS * 
FROM tb1
LIMIT 5";

$result = mysqli_query($link, $query);

$query = "SELECT FOUND_ROWS() AS count";
$result2 = mysqli_query($link, $query);

$row = mysqli_fetch_array($result2);

echo $row['count'];

您真的认为从表中选择所有行比计算它们快吗?
Myisam在表的元数据中存储了许多记录,所以从表中选择COUNT(*)不必访问数据。