mysql php无法获取外键值

Question

Hello I have a problem with my php code.. there are 3 tables for a recruitment system.

CREATE TABLE IF NOT EXISTS `members` (
   `uid` int(11) NOT NULL AUTO_INCREMENT,
   `username` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
   `password` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
   `cpassword` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
   `email` varchar(30) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
   `role` varchar(30) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
   PRIMARY KEY (`uid`)'
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=60 ;   

The candidate table :

CREATE TABLE IF NOT EXISTS `candidate` (
  `fullname` varchar(35) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `webpage` varchar(150) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `tel` int(35) NOT NULL,
  `nationality` varchar(35) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `position` varchar(30) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `interviewed` varchar(30) NOT NULL DEFAULT 'No',
  `rating` varchar(30) NOT NULL,
  `c_id` int(11) NOT NULL AUTO_INCREMENT,
  `uid` int(11) NOT NULL,
  PRIMARY KEY (`c_id`),
  KEY `uid` (`uid`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=135 ;

The academic table :

CREATE TABLE IF NOT EXISTS `academic_candidate` (    
    `degree` varchar(30) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `exp_years` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `comment1` varchar(300) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `proposed_positions` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `research_years` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `comment2` varchar(300) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `department` varchar(25) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
    `a_id` int(25) NOT NULL AUTO_INCREMENT,
    `uid` int(11) NOT NULL,
    `c_id` int(11) NOT NULL,
    PRIMARY KEY (`a_id`),
    UNIQUE KEY `id` (`a_id`),
    KEY `uid` (`uid`),
    KEY `c_d` (`c_id`),
    KEY `c_id` (`c_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=40 ;`

-- Constraints for table academic_candidate

ALTER TABLE academic_candidate ADD CONSTRAINT academic_candidate_ibfk_1 FOREIGN KEY ( uid ) REFERENCES members ( uid ) ON DELETE CASCADE ON UPDATE CASCADE, ADD CONSTRAINT academic_candidate_ibfk_2 FOREIGN KEY ( c_id ) REFERENCES candidate ( c_id ) ON DELETE CASCADE ON UPDATE CASCADE;

--

-- Constraints for table candidate

ALTER TABLE candidate ADD CONSTRAINT candidate_ibfk_1 FOREIGN KEY ( uid ) REFERENCES members ( uid ) ON DELETE CASCADE ON UPDATE CASCADE;

--

Now, I use this query in order to store the values in the table academic_candidate

session_start();

    $query = "SELECT * FROM academic_candidate WHERE degree = '$degree'";
$result = mysql_query($query);
$count  = mysql_num_rows($result);

if($count > 0){ 
    echo "You ALready complete the form </br>";
    header("Location:../candidate/candidate_index.php");
}
else{
        $degree =($_POST['degree']);
        $exp_years = ($_POST['exp_years']);
        $comment1 = ($_POST['comment1']);
        $proposed_positions = ($_POST['proposed_positions']);
    $research_years=($_POST['research_years']);
    $comment2=($_POST['comment2']);
    $department=($_POST['department']);

   $uid=($_SESSION['uid']);


    $query1 = "INSERT INTO academic_candidate

                (degree,exp_years,comment1,proposed_positions,research_years,comment2,department,uid,c_id)
                SELECT
                 '$degree','$exp_years','$comment1','$proposed_positions','$research_years','$comment2','$department','$uid','$c_id'
                    FROM  candidate         
                 WHERE  uid='$uid' AND c_id='$c_id'  ";


    $result = mysql_query($query1);

    if(!$result){
        echo "Error";
        die (mysql_error());                                          
    }   

    else{
        header("Location:../candidate/view_application.php");
    }

}

My problem is that stores all the values on the table academic_candidate table but the c_id is 0 . What can I do in order to take the candidate.c_id?

Answer 1

You're passing literal values to your INSERT INTO statement.

Consider the difference:

SELECT 'bar' FROM foo;

SELECT bar FROM foo;

Here's a demo on SQLFiddle.

Looking at your query:

SELECT '$degree'

Is not the same as:

SELECT degree

One of these is simply echoing whatever value you pass in, the other is actually selecting a column from the DB.