MySQL query is creating a duplicate row

Question

I have never encountered an error like this before. I was using prepared statements when it stared and have tried everything to correct the problem including stripping the form down to it's bare components.

The following code, when executed, is creating a duplicate row.

    $sql = "INSERT INTO inventory 
    VALUES  ('','$stocknum','$year','$make','$model','$price','$body','$mile','$engine','$trans',
    '$drive','$doors','$fuel','$vin','$des','$featured','$sale','$features','$safety','$airbags','$power',
    '$exterior','$interior','','','','','')";
$insert = mysql_query($sql,$connection) or die(mysql_error());
$name = mysql_insert_id();

I can't wrap my head around why it would do this.

Answer 1

The insert statement is possibly getting called twice. Did you add logging to make sure this code is only running once? And did you search to make sure there's no other code to add inventory records anywhere else?

Answer 2

When you query the table afterwards, are you only selecting from this table or are you perhaps joining it to another table? If you have more than one child record in the joined table you will get multiple results.

Your code looks correct to me, unless there is something in the rest of the page I'm not seeing.

Answer 3

How many columns are in the inventory table? Is the second row an exact duplicate of the first? I don't know PHP's DB interface but I could envision a bug where, if you give it more fields than there are columns, it attempts to create multiple rows.

EDIT: A little research on the MySQL documentation finds:

INSERT statements that use VALUES syntax can insert multiple rows. To do this, include multiple lists of column values, each enclosed within parentheses and separated by commas. Example:

INSERT INTO tbl_name (a,b,c) VALUES(1,2,3),(4,5,6),(7,8,9);

The values list for each row must be enclosed within parentheses. The following statement is illegal because the number of values in the list does not match the number of column names:

INSERT INTO tbl_name (a,b,c) VALUES(1,2,3,4,5,6,7,8,9);

Depending on the contents of your variables and how the PHP/MySQL driver handles those variables (direct text substition or ? placeholders) the statement being executed may not look like you expect. Try displaying the value of $sql before you execute it.

Answer 4

I'd guess you have a problem with an .htaccess file which is making 2 requests to the same script. Log a message with a timestamp when you do your insert.