SQL Query出了什么问题？ [英] What's wrong with SQL Query?

问题描述

Hello Codeproject，



这是我学习HTML，SQL和PHP的前两周。我刚刚完成了关于简单注册/登录系统的教程。然而，简单性带来了成本;他们没有告诉你如何检查用户名是否已经存在。



注册和登录工作正常，但是，如果用户名存在，我实施支票时遇到麻烦。



这是我遇到麻烦的代码：

Hello Codeproject,

It's my first two weeks of learning HTML, SQL, and PHP. I just finished following a tutorial on a simple register/login system. The simplicity however came with a cost; they did not show you how to check if a username already exists.

The registering and logging in works, but, I'm having troubles implementing my check if username exists.

This is the code that I'm having troubles with:

$sql="SELECT FROM members WHERE username=123";
if(mysql_num_rows($sql)>=1)
{
    echo"name already exists";
}
else

这是注册用户的代码（在上面的代码之后）：

This is the code that registers the user(After the above code):

{
           // Fields are clear, add user to database
   // Setup query
   $q = "INSERT INTO `members` (`username`,`password`,`email`) "
   ."VALUES ('".$_POST["username"]."', "
   ."PASSWORD('".$_POST["password"]."'), "
   ."'".$_POST["email"]."')";
   // Run query
   $r = mysql_query($q);
   // Make sure query inserted user successfully
   if ( !mysql_insert_id() )
   {
   die("Error: User not added to database.");
   }
   else
   {
   // Redirect to thank you page.
   Header("Location: register.php?op=thanks");
   }
   } // end if
   }

有人能告诉我选择来自查询的错误吗？我注册了大约20个帐户，用户名为123，看看是不是我弄乱了用户名输入，但仍然没有运气！



编辑：傻傻的我！我忘了使用mysql_query（），这从来没有从我的数据库中得到任何结果。固定代码：

Could anyone tell me what I'm doing wrong with the "select from" query? I registered around 20 accounts with the username as "123" to see if it was just me messing up the username input, but still no luck!

Edit: Silly me! I forgot to use mysql_query(), this would have never given any result from my database. Fixed code:

$sql=mysql_query("SELECT * FROM `members` WHERE `Username` = 123");
			if(mysql_num_rows($sql) != 0)    {
				echo"name already exists";
			} else    {}

祝你好运，

- Dimitri

Best regards,
- Dimitri

推荐答案

sql = SELECT FROM members WHERE username = 123;
if（mysql_num_rows（

sql="SELECT FROM members WHERE username=123"; if(mysql_num_rows(

sql）> = 1）
{
echo 名称已存在;
}
其他

sql)>=1) { echo"name already exists"; } else

这是注册用户的代码（在上面的代码之后）：

This is the code that registers the user(After the above code):

{
           // Fields are clear, add user to database
   // Setup query
   

q = INSERT INTO`member`（`username`，`password`，`email`）
。 VALUES（'。

这篇关于SQL Query出了什么问题？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！