check for duplicates and prevent them from being added to a DB

[koolaidman52]

im coding a database of cartoon series for my site, where users can sign up and add, edit, and do someother stuff with cartoons series, i have a page addseries.php and i have some problem code in the file:

[code]
...
$que = @mysql_query("SELECT series_title FROM series WHERE series_title = $_POST[title]");
if (mysql_num_rows($que) == 0)
{
$que = "INSERT INTO series (series_title, creator, begin_year, end_year, seasons, station , series_description ) VALUES ('$_POST[title]', '$_POST[creator]', '$_POST[begin_year]', '$_POST[end_year]', '$_POST[seasons]', '$_POST[station]', '$_POST[description]')";
@mysql_query($que, $connection);
$spam = @mysql_query($que, $connection);
if ($spam)
{
  echo "<p>Added series</p><br />";
}
                                                   }
else
{
echo "That series already exists in the database";
echo $add_series;
                                                                }
...
[/code]
the user supplies $_POST[title]', '$_POST[creator]', '$_POST[begin_year]', '$_POST[end_year]', '$_POST[seasons]', '$_POST[station]', '$_POST[description] (im lazy, i just did a copy and paste).

i was testing the page with "captain planet" as $_POST[title], and i found that im able to continue adding as many "captain planets" as I want (I never get  "That series already exists in the database"). obviosly my code is not working, but I can't fgure out why.

any of you wizards know what i'm doing wrong?

ps im also getting
"Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\Program Files\Apache Group\Apache2\htdocs\omnibase\addseries.php on line 47"
too

[akitchin]

give this query a shot:

[code]"SELECT series_title FROM series WHERE series_title = '{$_POST['title']}'"[/code]

when you get an invalid resource error, it's usually an indicator that your query failed.  in that case, add an or die(mysql_error()) to the offending query to see what the problem is.  it's useful for debugging, but can easily be removed once you've got everything working.

[Drumminxx]

The warning is telling you that your query is bad:

[code]
$que = @mysql_query("SELECT series_title FROM series WHERE series_title = $_POST[title]");
[/code]

make sure the field names are correct and are you checking that the user always gives $_POST['title'] a value?

[code]
$title = $_POST['title'];
$que = @mysql_query("SELECT series_title FROM series WHERE series_title = '$title'");
[/code]

The above will make it easier to debug, if neccessary, when you have alot of code to search through

[pixy]

This wont give a nice message to the user, but place a UNIQUE index on the series_title column. That way it wont let duplicates be entered.

[koolaidman52]

oh thats clever pixy, maybe version 0.2, it won't be implemented for a few months because i still have to work out some session issues and user authentication/ registration stuff

anyway, what the first dude said worked but ill keep the UNIQUE thing in mind