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mysqli sElECt Count

优化总结: 1.任何情况下select COUNT(*) from xxx 是最优选择; 2.尽量减少select COUNT(*) from xxx where col = ‘xxx’ 这种查询; 3.杜绝select COUNT(col) from tablename where col = ‘xxx’ 的出现。(其中col非主键) 环境: MySQL版本:5.0...

据php手册的相关资料,mysql_fetch_row 比 mysql_fetch_array 稍快。 示例代码如下: $query = "select count(*) from test where testid=".$_POST['testid']; $result=mysql_query($query); list($num) = mysql_fetch_row($result);

取值示例代码如下:

数据表不存在~你是不是搬家了没有从新安装啊 ~或者你的空间支持么?

mysql_query 的返回值不是查询出来的结果的条数,而是返回本次查询是否成功。 如果失败则返回flase 用来做判断,例如下面的用法: $res=mysql_query($sql);if ($res){ $row=mysql_fetch_array($res);}撸主在学习的过程中,需要多多注意每个函数...

$query =mysqli_query($con, 'select count(*) from demo'); echo mysqli_result($query, 1);// 建议,mysqli扩展是mysql的oo思想,所以建议使用如下: 1 2 3 4 5 6 7 8 9 10 $mysqli = new mysqli("localhost", "root", "123", "demo");//连接...

子查询中select count(1) as num from A where A.ID = B.ID 就是统计B表和A表用ID连接的行数 子查询的行数=0,就可以实现从B表中排除A表数据

$query =mysqli_query($con, 'select count(*) from demo');echo mysqli_result($query, 1);// 建议,mysqli扩展是mysql的oo思想,所以建议使用如下: $mysqli = new mysqli("localhost", "root", "123", "demo");//连接本地demo数据库if (mysql...

SELECT d.*,pm.label, ( SELECT COUNT(*) from (select js,jifen from deal where uid=m.id and time>DATE_FORMAT(time,'$Y-$d-$m') and state!=1 and state!=6 GROUP BY stoptime ) ) as jys from deal as d,members as m,pricemsg as pm where...

result没问题的吧, 多斜杠那一行改成:$row=$result->fetch_row(); 试试。

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