php mysql从数据库检索单个值

Question

Hey guys this is a really noob question but for some reason I can't seem to get a single value from a database.

Here is the code that I'm using:

$stmt = $pdo->prepare("SELECT column FROM teacher WHERE id = :id")
$stmt->bindParam(':id', $id);
$stmt->execute();

$oldValue = $stmt->fetchColumn();

I do filter the variables before in the code because I got them in this file as post data, here's the code for that part:

$column = filter_input(INPUT_POST, "column", FILTER_SANITIZE_STRING);
$id = filter_input(INPUT_POST, "id", FILTER_SANITIZE_STRING);
$value = filter_input(INPUT_POST, "value", FILTER_SANITIZE_STRING);

In this same file updating the database works so its probably not a problem with connecting to the database. Please help! Thanks

Full error from $stmt:

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'column FROM teacher WHERE id = ?' at line 1' in /var/www/duties/testTableDataUpload.php:25Stack trace:#0 /var/www/duties/testTableDataUpload.php(25): PDO->prepare('SELECT column F...')#1 {main} thrown in /var/www/duties/testTableDataUpload.php on line 25

Answer 1

I know this is not an answer, just trying to post code to OP.

jquery:

var data="id="+id;
        $.ajax({
            type:"POST",
            data: data,
            url:"somePHPdbPage.php",
            success: function(result){
            $('#blah').html(result);
            }
    });

Then somewhere on your main page do:

 <div id='blah'></div>

what this will do is add the result to the div blah. and you should plainly see it on your main page. then c/p all you want. Have to head out for a bit. will check back in.

and on your php page:

$stmt = $pdo->prepare("SELECT column FROM teacher WHERE id = :id")
$stmt->bindParam(':id', $id);
$stmt->execute();
print_r($stmt->errorInfo());

Answer 2

column is a reserved word in MySQL and must be escaped using '`'. You are also missing a semicolon at the end of the line. Try the following:

$stmt = $pdo->prepare("SELECT `column` FROM teacher WHERE id = :id");
$stmt->bindParam(':id', $id);
$stmt->execute();

$oldValue = $stmt->fetch();

Answer 3

maybe the problem be with your data but if there be duplicated data you can use one of the belows:

$stmt = $pdo->prepare("SELECT distinct column FROM teacher WHERE id = :id")

or

$stmt = $pdo->prepare("SELECT column FROM teacher WHERE id = :id limit 1")

Answer 4

If you have a column in the teach tabled named 'first_name' you should be able to do the following

$stmt = $pdo->prepare("SELECT first_name FROM teacher WHERE id = :id ORDER BY id DESC limit 1")
$stmt->bindParam(':id', $id);
$stmt->execute();

$row = $stmt->fetch(PDO:FETCH_ASSOC);
echo $row['first_name']; //Will print out the first name (if that is a column in your table of course)