mysql 行锁解决高并发
for update 必须在事务中执行
(避免高并发时库存为负数)
where条件有主键是行锁 否则是表锁
$pdo = new PDO('mysql:host=127.0.0.1;port=3306; dbname=test','root','123456');
$pdo->beginTransaction();//开启事务
$sql="select `number` from storage where id=1 *for UPDATE* ";//利用for update 开启行锁
$res = $pdo->query($sql)->fetch();
$number = $res['number'];
if($number>0)
{
$sql ="insert into `order` VALUES (null,$number)";
$order_id = $pdo->query($sql);
if($order_id)
{
$sql="update storage set `number`=`number`-1 WHERE id=1";
if($pdo->query($sql))
{
$pdo->commit();//提交事务
}
else
{
$pdo->rollBack();//回滚
}
}
else
{
$pdo->rollBack();//回滚
}
}