Mysql“where”和“or”语句

Question

我开始研究一个Mysql查询，它不断出现错误？

有人可以看一下并告诉我我做错了什么吗？

$query = ("select * from `users` where (`username`='$username' and `password`='$password' or select * from `users` where `$username `='$email' and `password`='$password')");

错误是

 mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/a8423624/public_html/testchecklogin.php on line 57

这意味着它没有找到任何人。这意味着我的查询错了吗？

Answer 1

... OR SELECT...发出错误。我想你是想把它写成：

$query = ("select * from `users` where (`username`='$username' OR `$username `='$email') and `password`='$password'");

Answer 2

尝试此查询：

select * from `users` 
where 
(`username`='$username' or `username `='$email') and `password`='$password'

Answer 3

作品！

SELECT * FROM "users" WHERE (username = '".$username."' OR username = '".$email."') AND password = '".$password."'";