[SOLVED] How to check that there are no values already in a database field?

[dessolator]

Hi, I was wondering how I would check that there are no values already in the database? with php and mysql

 

Basically what I'm doing is a games system where people play 3 games, and when I create a fixture I want it to check that there are no values already in the database for those users (users are identified by a unique ID) Iif there are entries display error message if not execute insert into database statement.

 

Here is my code so far:

 

fixtureform.php

 

<?php  
$host="localhost"; // Host name
$username="root"; // Mysql username
$password="abc123"; // Mysql password
$db_name="games_db1"; // Database name
$tbl_name="members"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
?>
<form id='form1' name='form1' method='post' action='gameprocessform.php'>
<center>
<b>Arrange a match</b><br/ ><br/ >
<select name='select'>
<?php
//FIRST DROP DOWN
echo "<center>";
//Database - Assigns the below statement into the variable query
$query = "SELECT id, forename, surname, class, house FROM members WHERE house = 'yellow' AND permissions ='3'";
$result = mysql_query($query);
//$row = mysql_fetch_row($result);
while($row = mysql_fetch_array($result))
  {
echo"<option style='background: yellow' value='$row[0]'>Name: $row[1] $row[2] | Class: $row[3] | House: $row[4]</option>";
}
echo "</center>";


$query1 = "SELECT id, forename, surname, class, house FROM members WHERE house = 'green' AND permissions ='3'";
$result1 = mysql_query($query1);
echo "<center>";
while($row = mysql_fetch_array($result1))
  {
echo"<option style='background: green' value='$row[0]'>Name: $row[1] $row[2] | Class: $row[3] | House: $row[4]</option>";
}
echo "</center>";
?>
</select>

<br/ >VS<br/ >


<select name='select1'>
<?php
//SECOND DROP DOWN
echo "<center>";
//Database - Assigns the below statement into the variable query
$query2 = "SELECT id, forename, surname, class, house FROM members WHERE house = 'yellow' AND permissions ='3'";
$result2 = mysql_query($query2);
//$row = mysql_fetch_row($result);
while($row = mysql_fetch_array($result2))
  {
echo"<option style='background: yellow' value='$row[0]'>Name: $row[1] $row[2] | Class: $row[3] | House: $row[4]</option>";
}
echo "</center>";


$query3 = "SELECT id, forename, surname, class, house FROM members WHERE house = 'green' AND permissions ='3'";
$result3 = mysql_query($query3);
echo "<center>";
while($row = mysql_fetch_array($result3))
  {
echo"<option style='background: green' value='$row[0]'>Name: $row[1] $row[2] | Class: $row[3] | House: $row[4]</option>";
}
echo "</center>";
?>
</select>
</center>  


<?php 
//GAMES DROP DOWN 
$query = "SELECT game FROM games";
$result = mysql_query($query);
?>
<center>
<br/ >GAME<br/ >
<select name='select2'>
<?php
while($row = mysql_fetch_array($result))
  {

echo"<option style='background: blue'  value='$row[0]'>$row[0]</option>";
}
?>
</select>
  
  <br/ ><br/>  
  <input type="submit" value="Submit" />
  </center>
</form>
</body>
</html>

 

 

 

fixtureprocessform.php

 

<?php
ob_start();
$host="localhost"; // Host name
$dbusername="root"; // Mysql username
$password="abc123"; // Mysql password
$db_name="games_db1"; // Database name
$tbl_name="members"; // Table name

$first_student= substr($_POST['select'], 0, 99);
$second_student= substr($_POST['select1'], 0, 99);
$game=substr($_POST['select2'], 0, 99);

echo $first_student;
echo "\n";
echo $second_student;
echo "\n";
echo $game;
echo "\n";


if ($first_student == $second_student){
echo "Sorry you must select two different students, one from the yellow house and one from the green house.";
exit (0);
}
else{
//Getting house and class for first user from db and storing it in variables
mysql_connect("$host", "$dbusername", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

//Database - Assigns the below statement into the variable query
$query = "SELECT house, class FROM members WHERE id = '$first_student'";
$result = mysql_query($query);

if($row = mysql_fetch_array($result))
  {
   $firstuser_house = $row[0];
   $firstuser_class = $row[1];
}
else{
echo "No users returned";
}
echo $firstuser_house;
echo $firstuser_class;


//Getting house and class for SECOND user from db and storing it in variables
mysql_connect("$host", "$dbusername", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

//Database - Assigns the below statement into the variable query
$query = "SELECT house, class FROM members WHERE id = '$second_student'";
$result = mysql_query($query);

/*If there is a result (which there will only be 1 as the UID is a unique ID) 
assign the house and class values for the student in 2 separate variables*/
if($row = mysql_fetch_array($result))
  {
   $seconduser_house = $row[0];
   $seconduser_class = $row[1];
}
//If no user is found for that ID ecbo error message
else{
echo "No users returned";
}
echo $seconduser_house;
echo $seconduser_class;
}
//Validation so that people from the same class or house can't play each other
if ($firstuser_house == $seconduser_house){
echo "You cannot play someone from the same house";
exit (0);
}

if ($firstuser_class == $seconduser_class){
echo "You cannot play someone from the same class";
exit (0);
}

?>

 

 

 

Thanks,

 

Ian

 

[revraz]

There are two ways to check if it's empty.

 

One, you can use IF EMPTY

Two, you can use IF $x == ""

 

You can use either MYSQL or PHP to check if they are empty.