(1).创建数据库test ,创建表shop(字段id,total),商品id是1,商品总数10
(2).PHP模拟购买,商品数量大于0才能购买
<?php
//连接数据库
$con=mysqli_connect("192.168.2.186","root","root","test");
//查询商品数量是否大于0
$res=mysqli_fetch_assoc(mysqli_query($con,'SELECT total FROM shop WHERE id=1 LIMIT 1'));
if($res['total']>0){
mysqli_query($con,'UPDATE shop SET total=total-1 WHERE id=1');
}
unset($res);
mysqli_close($con);
?>(3).ab.exe进行高并发测试
ab -n 500 -c 500 http://test.cn/
(4).数据库结果:
高并发下这样完全不行
(5).我们可以使用where条件来处理，更新的时候加上where条件即可，更新的时候更新失败说明库存已经不足
<?php
//连接数据库
$con=mysqli_connect("192.168.2.186","root","root","test");
//查询商品数量是否大于0
$res=mysqli_fetch_assoc(mysqli_query($con,'SELECT total FROM shop WHERE id=1 LIMIT 1'));
if($res['total']>0){
mysqli_query($con,'UPDATE shop SET total=total-1 WHERE id=1 and total>0');
}
unset($res);
mysqli_close($con);
?> 
