PHP和MySQL搜索栏的价值

Question

I am a little confused about how $query works and how I can find a value... Say I have a checkuser.php script. The purpose here is to echo "Correct" if the user already exists. I have the columns (username, password, email). What I want to know is how can I search the column username for value $username ? This is what I have currently:

$query = sprintf("SELECT * FROM users WHERE CONCAT(username) LIKE '$u'");
$result = mysql_query($query);
if(mysql_num_rows($result) != 1)
echo "Username Not Found";

Thanks!

Answer 1

I haven't tested it, but this should work:

$q=mysql_query("select ysername from user where username='$u'");
$count=mysql_num_rows($q);
If ($count>0) { echo "usename fount";};

Answer 2

In your query, you do not need to use the sprintf() function at all. an SQL query is inserted as a regular string.

Furthermore you don't need to use CONCAT() SQL function either.

Then if you want to check against an exact string you can just compare with the = operator instead of using SQL LIKE statement.

Answer 3

This should work. However, I didn't test it:

$query = "SELECT * FROM users WHERE username = '$u'";
$result = mysql_query($query);
if(mysql_num_rows($result) > 0)
echo "Username Not Found";