How to detect that username already use in the database

Question

<?php

if(isset($_POST["Add"]))    
{

$name=$_POST["Emp_Username"];
$pass=$_POST["Emp_Password"];
$fname=$_POST["Emp_Fname"];
$lname=$_POST["Emp_Lname"];
$hph=$_POST["ContactNo_Home"];
$hp=$_POST["ContactNo_HP"];
$mail=$_POST["Emp_Email"];
$add=$_POST["Emp_Address"];
$age=$_POST["Emp_Age"];
$pos=$_POST["Position"];
$dept=$_POST["Dept_ID"];

mysql_query("
    insert into employee(Dept_ID, Emp_Address, Emp_Age, 
    Position, >Emp_Username, Emp_Password, Emp_Fname, Emp_Lname, 
    ContactNo_Home, ContactNo_HP, Emp_Email) 
    >values('$dept','$add','$age','$pos','$name','$pass','$fname',
    '$lname','$hph','$hp','$mail'>)
   ");

?>    

<script type="text/javascript">
alert("Record saved.");    
</script> 

<?php } ?>

Use `UNIQUE` constraint on the username column in DB, in that case, insert with same username will fail (return an error). Then check for errors upon insert query. — poncha, Aug 26 '13 at 12:43
Possible [Duplicate](http://stackoverflow.com/questions/8611044/check-if-username-already-exists-in-database-mysql-php) — Som, Aug 26 '13 at 12:46

score 2 · Accepted Answer · answered Aug 26 '13 at 12:44

2

Create a unique key on username field, then detect error no 1062:

if (mysql_errno() == 1062) {
    print 'username taken!';
}

answered Aug 26 '13 at 12:44

Cups

6,901
3
26
30

score 1 · Answer 2 · answered Aug 26 '13 at 12:44

1

A simple SELECT query should suffice:

SELECT COUNT(employee.Emp_Username) AS num 
FROM employee 
WHERE Emp_Username = 'USERNAME';

answered Aug 26 '13 at 12:44

Wayne Whitty

19,513
7
44
66

Without a unique constraint at DB level, this is a race condition – Tom Regner Aug 26 '13 at 13:19
I know. But I based my answer on the assumption that the database is correctly designed. OP asked how to detect if the username is already detected. He didn't ask how to prevent duplicate usernames. – Wayne Whitty Aug 26 '13 at 14:22

score 0 · Answer 3 · answered Aug 26 '13 at 12:44

0

I hope this help you,

$query=mysql_query("select * from employee where Emp_Username=$name");
    $row=mysql_num_rows($query);
    if($row>0){
        echo 'user exist';
    }else{
        echo 'User not exist';
    }

answered Aug 26 '13 at 12:44

Prabhakaran

3,900
15
46
113

score 0 · Answer 4 · answered Aug 26 '13 at 12:59

0

Maybe you should validate field "user" with ajax before submit the form

$name = $_POST["Emp_Username"];
$results = mysqli_query($connecDB,"SELECT * FROM employee WHERE Emp_Username='$name'");
$name_exist = mysqli_num_rows($results);

if($username_exist) {
    echo 'busy';
}else{
    echo 'free';
}

answered Aug 26 '13 at 12:59

santyas

96
1
2
12

1

Without a unique constraint at DB level, this is a race condition. – Tom Regner Aug 26 '13 at 13:19
1

Two connections ask for a given username simultaneous , both get the answer 'name free' - both will register the name in the assumption it unique - without a unique constraint both will succeed. – Tom Regner Aug 26 '13 at 14:24

How to detect that username already use in the database

4 Answers4