mysql_fetch_array(): supplied argument is not a valid "Error"

[Wilson]

I keep getting the above error, and have went over the script a hundred times. Can anyone see where I have made my mistake? I have put where the error is received in bold and underline

"Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /home/XXXX/public_html/update.php on line 54"

$cid=mysql_connect ("localhost", "XXXX", "XXXXX) or die ('I cannot connect to the database because: ' . mysql_error());
mysql_select_db ("XXXX", $cid);
    # processed when form is submitted back onto itself
    if ($REQUEST_METHOD=="POST") {
        # setup SQL statement
        $SQL = " UPDATE books SET";
        $SQL = $SQL . " Book = '$Book', ";
        $SQL = $SQL . " Year = '$Year', ";
        $SQL = $SQL . " Author = '$Author', ";
        $SQL = $SQL . " Genre = '$Genre' ";
        $SQL = $SQL . " Number = '$Number' ";
        $SQL = $SQL . " Series = '$Series' ";
        $SQL = $SQL . " Complete = '$Complete' ";
        $SQL = $SQL . " Recommendation = '$Recommendation' ";
        $SQL = $SQL . " Status = '$Status' ";
        $SQL = $SQL . " WHERE id = $id ";
 
        # execute SQL statement
        $result = mysql_db_query($db,"$SQL",$cid);
        # check for errors
        if (!$result) { echo("ERROR: " . mysql_error() . "\n$SQL\n");    }
        echo ("<P><B> Link Updated</B></P>\n");
    }
    else { # display edit form (not post method)
        # setup SQL statement to retrieve link
        # that we want to edit
 
        $SQL = " SELECT * FROM books ";
        $SQL = $SQL . " WHERE id = $id ";
        # execute SQL statement
        $ret = mysql_db_query($db,$SQL,$cid);
        # retrieve values
        $row = mysql_fetch_array($ret); ( Point of error)
        $Book = $row["Book"];
        $Year = $row["Year"];
        $Author = $row["Author"];
        $Genre = $row["Genre"];
        $Number = $row["Number"];
        $Series = $row["Series"];
        $Complete = $row["Complete"];
        $Recommendation = $row["Recommendation"];
        $Status = $row["Status"];
?>

Of course there is a form that goes with it, that form shows up fine.
Thanks in advance.

[powerdesign]

first of all, why do you use mysql_db_query instead of mysql_query ?
the official documentation says that "This function is deprecated, do not use this function. Use mysql_select_db() and mysql_query() instead." (http://php.net/manual/en/function.mysql-db-query.php)

the second question is why do u use construction $result = mysql_db_query($db,"$SQL",$cid); 14 lines above and then $ret = mysql_db_query($db,$SQL,$cid); (here $SQL is not in "")

[Wilson]

Originally Posted by powerdesign

first of all, why do you use mysql_db_query instead of mysql_query ?
the official documentation says that "This function is deprecated, do not use this function. Use mysql_select_db() and mysql_query() instead." (http://php.net/manual/en/function.mysql-db-query.php)

the second question is why do u use construction $result = mysql_db_query($db,"$SQL",$cid); 14 lines above and then $ret = mysql_db_query($db,$SQL,$cid); (here $SQL is not in "")

I am not sure. This is a script that i am emulating to update or correct the database and it is copied from this website.

I have changed all that to this (got rid of the $db as well)
I still get the same error

if ($REQUEST_METHOD=="POST") {
        # setup SQL statement
        $SQL = " UPDATE `books` SET ";
        $SQL = $SQL . " Book = '$Book', ";
        $SQL = $SQL . " Year = '$Year', ";
        $SQL = $SQL . " Author = '$Author', ";
        $SQL = $SQL . " Genre = '$Genre' ";
        $SQL = $SQL . " Number = '$Number' ";
        $SQL = $SQL . " Series = '$Series' ";
        $SQL = $SQL . " Complete = '$Complete' ";
        $SQL = $SQL . " Recommendation = '$Recommendation' ";
        $SQL = $SQL . " Status = '$Status' ";
        $SQL = $SQL . " WHERE `Key` = $id ";
        # execute SQL statement
        $result = mysql_query($SQL,$cid);
        # check for errors
        if (!$result) { echo("ERROR: " . mysql_error() . "\n$SQL\n");    }
        echo ("<P><B> Link Updated</B></P>\n");
    }
    else { # display edit form (not post method)
        # setup SQL statement to retrieve link
        # that we want to edit
        $SQL = " SELECT * FROM `books` ";
        $SQL = $SQL . " WHERE Key = $Key ";
        # execute SQL statement
        $ret = mysql_query($SQL,$cid);
        # retrieve values
        $row = mysql_fetch_array($ret);
        $Book = $row["Book"];
        $Year = $row["Year"];
        $Author = $row["Author"];
        $Genre = $row["Genre"];
        $Number = $row["Number"];
        $Series = $row["Series"];
        $Complete = $row["Complete"];
        $Recommendation = $row["Recommendation"];
        $Status = $row["Status"];

[powerdesign]

an error like "mysql_fetch_array(): supplied argument is not a valid MySQL result" gets when you have no results from query, for example.

try to debug your actions, say put this
echo 'the query is: '.$SQL.'<br /> and error: '.mysql_error(); die;
after your
# execute SQL statement
$ret = mysql_query($SQL,$cid);

and see if there any errors with you request to DB.
also you get you query text - check it, and if you have phpmyadmin, try to paste it there and executr sql query from phpmyadmin - look if there any errors.

[Wilson]

Thanks, that helped greatly in finding the syntax errors, I can at least open the page with no errors!

You were a great help, thank you. I find these things are usually right in front of you and you cant see them through the window.