Multiple INSERT not working - php

Question

I have multiple If statements that if true, inserts data into the db. The Problem is that the 2nd one of the INSERT statements inserts it 4 times. How would i stop it from adding duplicates. Also the returned $_POST['tshirt'] contains only one value which is being inserted 4 times.
if(isset($_POST['distance'])) {
$dist = $_POST['distance'];
$sql="INSERT INTO sportevent_parameters.Distance(value, user_ref, event) VALUES ('$dist', '$id', '$event')";
}
mysql_query($sql, $con)
or die("MySQL Error: ".mysql_error());
if(isset($_POST['tshirt'])) {
$tshrt = $_POST['tshirt'];
$sql="INSERT INTO sportevent_parameters.T_Shirt(value, user_ref, event) VALUES ('$tshrt', '$id', '$event') ON DUPLICATE KEY UPDATE";
}
mysql_query($sql, $con)
or die("MySQL Error: ".mysql_error());
if(isset($_POST['partnerid'])) {
$sql="INSERT INTO sportevent_parameters.Partner_ID(value, user_ref, event) VALUES ('$partnerid', '$id', '$event')";
}
mysql_query($sql, $con)
or die("MySQL Error: ".mysql_error());
if(isset($_POST['racecategory'])) {
$sql="INSERT INTO sportevent_parameters.Race_Category(value, user_ref, event) VALUES ('$category', '$id', '$event')";
}
mysql_query($sql, $con)
or die("MySQL Error: ".mysql_error());
What would cause it to insert multiple copies into the DB?

Answer 1

Firstly, please sanitise your user input before using it directly in a query!!! - also read this.
Secondly - the problem is that your calls to mysql_query() should be inside the if statements. With what you have done, mysql_query() is executed regardless, only the SQL statement itself is changed by the if. This means that if the first if condition is true, but all the others are false, the first statement will be executed 4 times.
Change your code to:
if (isset($_POST['distance'])) {
$dist = mysql_real_escape_string($_POST['distance']);
$sql = "INSERT INTO sportevent_parameters.Distance(value, user_ref, event) VALUES ('$dist', '$id', '$event')";
mysql_query($sql, $con)
or die("MySQL Error: ".mysql_error());
}
// etc etc

Answer 2

Edit: The mysql_query's should be inside the if statements so it does not get called if the if is not called. I would also check the variables you are passing.
Multiple SQL statements in one query are not supported in PHP. You have to split up each SQL statement into separate queries to the database.
Link to PHP Manual: http://php.net/manual/en/function.mysql-query.php