Question

I have a small PHP Application which is supposed to allow a user to enter a 4 digit year into an XHTML web form and return all the information saved in the MySQL database with a lower year than the one provided. The years are stored in the db under the column yearPublished. I have the query working and I get no errors, however no data is being returned.

Here is the SQL file for creating the database:

CREATE TABLE IF NOT EXISTS `books` (
`ISBN` char(13) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
`title` varchar(40) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`author_firstName` varchar(40) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`author_lastName` varchar(40) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`genre` varchar(35) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`publisher` varchar(40) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`yearPublished` varchar(4) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`price` float DEFAULT '0.0',
PRIMARY KEY (`ISBN`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

And here is the PHP code that executes the query:

    if(isset($_POST['submitForm'])) {
    $strBookPubYear = $_POST['pubYear'];

    if(empty($strBookPubYear)) {
        print("<p class='error'>You must enter a 4 digit publication date!</p>\n");
    } else {
        if(!is_numeric($strBookPubYear)) {
            print("<p class='error'>The publication date must be numeric.</p>\n");
        } else {
            if(!(strlen($strBookPubYear) === 4)) {
                print("<p class='error'>The Publication date must be exactly 4 characters long.</p>\n ");
            } else {

        $sqlQuery = mysql_query("SELECT yearPublished FROM books WHERE yearPublished < '$strBookPubYear'");

        if($sqlQuery === false) {
            print("<p class='error'>Could not execute the query, please try again.</p>\n");
        } else {

notice the $sqlQuery variable that is supposed to get all the data where the yearPublished is lower than $strBookPubYear. I have read multiple tutorials on this, but they all are using the MySQL ‘Date’ data-type. In my case I am using a text data-type. Please do not tell me to use mysqli, this specific project does not require me to use mysqli.

Answer 1

Your yearPublished is stored as a varchar, which is essentially a string. Therefore, when you say yearPublished < '$strBookPubYear', it probably is not doing what you think that it is doing. Store yearPublished as an INTEGER. Either way it takes 4 bytes.

You can manually cast the varchar to a number in the query, and it should probably start working.

SELECT yearPublished FROM books WHERE (yearPublished+0) < '$strBookPubYear'

OK, that wasn’t really the problem! Try this error checking block, to spit out some better clues:

// Check result
// This shows the actual query sent to MySQL, and the error. Useful for debugging.
if (!$sqlQuery) {
    $message  = 'Invalid query: ' . mysql_error() . "\n";
    die($message);
}