php代码运行报错

Question

Warning: mysqli_query() expects at least 2 parameters, 1 given in D:\phpstudy_pro\WWW\allusers.php on line 31Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in D:\phpstudy_pro\WWW\allusers.php on line 33

下面是代码

//查询数据表中的所有数据

$result=mysqli_query("SELECT * FROM users BY id DESC");

//获取数据表的数据条数

$dataCount=mysqli_num_rows($result);

//echo $dataCount;

//打印输出所有数据