php - mysql_num_rows() 根本不工作

Question

我有这段 PHP 代码:

<?php
$username=$_POST['username'];
$password=$_POST['password'];

if($username&&$password){
$connect=mysql_connect("localhost","root","") or die(" Couldnt connect");
mysql_select_db("phplogin") or die ("Can't find database" .mysql_error());  
$query=mysql_query("SELECT * users WHERE username='$username' ");
$numrows=mysql_num_rows($query);
if (!$query) {
die('Invalid query: ' . mysql_error());
}
}
else
die ("Enter username and password!") .mysql_error();
?>

但是，当我尝试运行这段代码时，出现了这些错误:

Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\wamp\www\PHP testing\login.php on line 9

和

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'users WHERE username='alex'' at line 1

有人可以向我解释我在这里做错了什么吗？

Answer 1

您必须使用 FROM 关键字指定要从中选择的表:

$query=mysql_query("SELECT * FROM users WHERE username='$username' ");
$numrows=mysql_num_rows($query);