设置外键

Question

I was trying to set a foreign key so that I can associate the author of the photo to the username of users table , but I'm unable to create table.

UPDATE I got the unable to create table error resolved but the data still doesn't get in to the tables.

CREATE TABLE IF NOT EXISTS `users` (
`username` varchar(30) NOT NULL ,
`password` varchar(40) default NULL,
`usersalt` varchar(8) NOT NULL,
`userid` varchar(32) default NULL,
`userlevel` tinyint(1) unsigned NOT NULL,
`email` varchar(50) default NULL,
`timestamp` int(11) unsigned NOT NULL,
`actkey` varchar(35) NOT NULL,
`ip` varchar(15) NOT NULL,
regdate` int(11) unsigned NOT NULL,
PRIMARY KEY  (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;



CREATE TABLE IF NOT EXISTS photos (
ref int(10) unsigned NOT NULL auto_increment,
    photo varchar(75),
Firstname varchar(35),
    Lastname varchar(35),
    Age INT(3),
    author varchar(30) NOT NULL,
PRIMARY KEY (ref)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

here is what I tried to add FK after creating the table..

ALTER TABLE photos
ADD CONSTRAINT FK_photos
FOREIGN KEY (author) REFERENCES users(username)
ON UPDATE CASCADE
ON DELETE CASCADE;

here is the code to insert photo and some info along with it to database...

<?php
include("/include/session.php");
if(!$session->logged_in){ header("Location: ../main.php"); } else {
}
?>



<?php
$sub=0;

ini_set( "display_errors", 0);
if(isset($_REQUEST['submited'])) {
// your save code goes here

$allowedExts = array("jpg", "jpeg", "gif", "png");
$extension = end(explode(".", $_FILES["file"]["name"]));
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/png")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 2097152)
&& in_array($extension, $allowedExts))
{
if ($_FILES["file"]["error"] > 0)
{
echo "Return Code: " . $_FILES["file"]["error"] . "<br>";
}
else
{
echo "";
if (file_exists("pictures/" . $_FILES["file"]["name"]))
{
echo "<font size='4' color='red'><b>We are sorry, the file you trying to upload already exists.</b></font>";
  }

else
{
move_uploaded_file($_FILES["file"]["tmp_name"],
"pictures/" . $_FILES["file"]["name"]);
$sub= 1;
$mysqli = new mysqli("localhost", "root", "", "secure_login");

// TODO - Check that connection was successful.

$photo= "pictures/" . $_FILES["file"]["name"];
$fname = $_POST["fname"];
$lname = $_POST["lname"];
$age   =$_POST["age"];
$stmt = $mysqli->prepare("INSERT INTO photos (photo, Firstname, Lastname, Age) VALUES (?, ?, ?, ?)");

// TODO check that $stmt creation succeeded

// "s" means the database expects a string
$stmt->bind_param("ssss", $photo, $fname, $lname, $age);

$stmt->execute();

$stmt->close();

$mysqli->close();



echo "<font size='7' color='white'><b> Success! Your item has been listed.</b></font>";
echo '<meta http-equiv="refresh" content="2;url=home.php">';
}

}
}
else
{
echo "<font size='4' color='red'><b>We are sorry, the file you trying to upload is not an image or it exceeds 2MB in size.</b></font><br><font color='blue'><i>Only images under size of 2MB are allowed</i></font>.";
}
}


?>

<form action="" method="post" enctype="multipart/form-data">
<input type="hidden" name="submited" value="true" />


<?php
ini_set( "display_errors", 0);
if($sub==0)
{
?> 
<label  for="file"><font  size="5"><b>Choose Photo:</b></font></label>
<input id="shiny" type="file" name="file" onchange="file_selected = true;" required><br>
Last Name:<input  type="text" name="fname" value="<?php echo (isset($_POST['fname']) ? htmlspecialchars($_POST['fname']) : ''); ?>"required><br> 
Last Name:<input  type="text" name="lname" required><br> 
Age:<input type="text" name="age" required><br>
<input id="shiny" type="submit" value="Submit" name="submit">
<?php
}
?>


</form>
</div>

Answer 1

Do yourself a big favor and use an Integer as an ID field on all your tables and use that as your primary key field. Then have all of your foreign key constraints reference that. See the first example in the MySQL docs here: http://dev.mysql.com/doc/refman/5.5/en/example-foreign-keys.html

Plus, post your error message and I'll update my answer.

Answer 2

CREATE TABLE IF NOT EXISTS users ( username varchar(30) NOT NULL , password varchar(40) default NULL, usersalt varchar(8) NOT NULL, userid varchar(32) default NULL, userlevel tinyint(1) unsigned NOT NULL, email varchar(50) default NULL, timestamp int(11) unsigned NOT NULL, actkey varchar(35) NOT NULL, ip varchar(15) NOT NULL, regdate int(11) unsigned NOT NULL, PRIMARY KEY ( username ) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE IF NOT EXISTS photos ( ref int(10) unsigned NOT NULL auto_increment, photo varchar(75), Firstname varchar(35), Lastname varchar(35), Age INT(3), author varchar(30) NOT NULL, PRIMARY KEY (ref) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

A few changes, but otherwise works for me. But try to set foreign key on id column, not varchar.

Answer 3

It looks like your table definition needs a comma after photo varchar(75)

CREATE TABLE IF NOT EXISTS photos (
    ref int(10) unsigned NOT NULL auto_increment,
    photo varchar(75),
    Firstname varchar(35),
    Lastname varchar(35),
    Age INT(3),
    author varchar(30) NOT NULL,
PRIMARY KEY (ref)

) ENGINE=InnoDB DEFAULT CHARSET=latin1;