控制变量法-初中物理-Nobel Lecture, December 12, 1929-php执行SET GLOBAL connect_timeout=2效果

     $link = mysqli_connect("localhost", "wu", "wp", "wdb");
     $sql = 'SET GLOBAL  connect_timeout=2';
     mysqli_query($link, $sql);

     ini_set('memory_limit', '-1');
     $sql ='ww';
 $ww =0;
     if ($result = mysqli_query($link, $sql)) {
         while ($row = mysqli_fetch_assoc($result)) {
             echo '<br>',$ww,'--'.time();
             $ww++;
         }
         mysqli_free_result($result);
     }
 die();

     $link = mysqli_connect("localhost", "wu", "wp", "wdb");
     //$sql = 'SET GLOBAL  connect_timeout=2';
     //mysqli_query($link, $sql);

     ini_set('memory_limit', '-1');
     $sql ='ww';
 $ww =0;
     if ($result = mysqli_query($link, $sql)) {
         while ($row = mysqli_fetch_assoc($result)) {
             echo '<br>',$ww,'--'.time();
             $ww++;
         }
         mysqli_free_result($result);
     }
 die();

SHOW VARIABLES LIKE '%out%';

SET GLOBAL  connect_timeout=31536000;
SHOW VARIABLES LIKE '%out%';

SET GLOBAL  connect_timeout=2;
SHOW VARIABLES LIKE '%out%';

Navicat

'ww'

root账户 用php、Navicat、\MySQL\bin\mysql.exe 执行

SET GLOBAL  connect_timeout=420

影响的是每一个database，尽管php连接的是指定的某个库，Navicat是某个库的查询窗口，shell-mysql.exe USE w;