PHP没有将一些值插入MySQL数据库

Question

I have an HTML form which submits values to the following PHP file, which inserts them into a MySQL database:

<?php
  $con = mysql_connect("*","*","*");
  if (!$con)
    {
    die('Could not connect: ' . mysql_error());
    }

  mysql_select_db("*", $con);

  $sql="INSERT INTO scores (hometeam, awayteam, result)
  VALUES
  ('" . mysql_real_escape_string($_POST['hometeam']) . "',
   '" . mysql_real_escape_string($_POST['awayteam']) . "',
   '" . mysql_real_escape_string($_POST['result']) . "')";

  if (!mysql_query($sql,$con))
    {
    die('Error: ' . mysql_error());
    }
  echo "1 record added";

  mysql_close($con);
?>

Sometimes an input field in the HTML form will be left blank and in this case I do not want anything inserted into the database. I want the value to remain NULL. At the moment when I fill in my form like this:

Home team: Blue team
Away team: [blank]
Result: Won

The following is inserted into my database:

Home team: Blue team
Away team: ' '
Result: Won

What I want to be inserted/not inserted is:

Home team: Blue team
Away team: NULL
Result: Won

I've hunted hours for a solution. Can anyone help? Thank you.

Answer 1

if (!empty($_POST['hometeam'])) {
  $sql="INSERT INTO scores (hometeam) VALUES ('" . $_POST['hometeam'] . "')";
}

Notice the single quotes around the 'hometeam' part. You should also clean that using mysql_real_escape_string($_POST['hometeam']).

Bear in mind this will create upto 3 rows for each call, if you want to have a row like scores (hometeam, awayteam, result) you'll need to construct your query differently (i.e. a single query not 3 seperate ones).