我想选择表中的最高值:
$max = "SELECT MAX(pid) FROM pic";
然后将该值传递到PHP变量中:
$results_max = $conn->query($max);
$highest_val = $results_max->fetch_assoc();
然后在SQL插入语句中再次使用:
$sql_update = "UPDATE users
SET username = '$username', pid = '$highest_val'
WHERE username = '$username'";
然而,我测试了从第一个select语句($highest_val
)中得到的值,它返回"Array"
。有人知道我做错了什么吗?
编辑:
$sql_update = "UPDATE users
SET username = '$username', pic_id = '$highest_val[pid]'
WHERE username = '$username'" ;
您需要创建MAX(pid);
的别名
$max = "SELECT MAX(pid) as pid FROM pic";
现在您使用获取最大pid
$results_max = $conn->query($max);
$highest = $results_max->fetch_assoc();
$highest_val =$highest['pid'];// pass column name here
您的更新查询将是
$sql_update = "UPDATE users
SET username = '".$username."', pid = '".$highest_val."'
WHERE username = '".$username."'";