Detailed explanation of the steps for PHP to use PDO to operate mysql to read data-PHP Tutorial-php.cn

Detailed explanation of the steps for PHP to use PDO to operate mysql to read data

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Release： 2023-03-26 11:52:01

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This time I will bring you a detailed explanation of the steps for using PHP to operate mysql to read data. What are the precautions for using PHP to operate mysql to read data? The following is a practical case, let's take a look.

Preface

This article mainly introduces the relevant content about PHP using PDO to read large amounts of data from mysql, and share it for your reference and study , not much to say below, let’s take a look at the detailed introduction.

Environment

mysql: 5.6.34
php: 5.6
nginx: php-fpm

Applicable scenarios

Need to process a certain data set business

Business export of reading certain data from mysql
Need to process a certain mysql business operation update, delete, etc.
More operations that require processing a certain data set

pdo key settings

$dbh = new \PDO($dsn, $user, $pass);
# 关键设置，如果不设置，php依旧会从pdo一次取出数据到php
$dbh->setAttribute(\PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);
//perpare里的游标属性不是必须的
$sth = $dbh->prepare("SELECT * FROM `order`", array(\PDO::ATTR_CURSOR => \PDO::CURSOR_SCROLL));
$sth->execute();

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Generate

Generator, iterative data operation

This generator can be omitted

Try code

class Test {
 public function test()
 {
  set_time_limit(0);
  $dbms=&#39;mysql&#39;;  //数据库类型
  $host=C(&#39;DB_HOST&#39;); //数据库主机名
  $dbName=C(&#39;DB_NAME&#39;); //使用的数据库
  $user=C(&#39;DB_USER&#39;);  //数据库连接用户名
  $pass=C(&#39;DB_PWD&#39;);   //对应的密码
  $dsn="$dbms:host=$host;dbname=$dbName";
  $dbh = new \PDO($dsn, $user, $pass);
  $dbh->setAttribute(\PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);
  $sth = $dbh->prepare("SELECT * FROM `order`");
  $sth->execute();
  $i = 0;
  $newLine = PHP_SAPI == &#39;cli&#39; ? "\n" : &#39;<br />&#39;;
  foreach ($this->cursor($sth) as $row) {
//   var_dump($row);
   echo $row[&#39;id&#39;] . $newLine;
   $i++;
  }
  echo "消耗内存：" . (memory_get_usage() / 1024 / 1024) . "M" . $newLine;
  echo "处理数据行数：" . $i . $newLine;
  echo "success";
 }
 public function cursor($sth)
 {
  while($row = $sth->fetch(\PDO::FETCH_ASSOC)) {
   yield $row;
  }
 }
}
$test = new Test();
$test->test();

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Output

1
... //省略部分id
804288
消耗内存："0.34918212890625M
处理数据行数：254062
success

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I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!