SELECT Query不适用于MySQL

Question

I can't seem to make my query work. When I use $sth->execute(); I do get a reading, yet is pretty worthless for my goal as far as I know. If I use query, nothing shows up. Keep in mind that I'm a beginner when it comes to coding. Also, this is a school project and nothing more.

I don't know why the first line of code won't be implemented so look at the row below as part of the code:

$team1 = $_POST['teamname'];
$sth = $pdo->prepare("SELECT odds1 FROM odds WHERE :team1=team1");
$sth->bindParam(':team1', $team1);
$sth->query();
$values = $sth->fetchAll(PDO::FETCH_ASSOC);                 
echo $values[odds1];

Answer 1

This code should be crashing with errors, so if you're wondering why it "doesn't work" the first place to check is your error log. PHP will output all kinds of warnings and errors there that help with your debugging, so if you don't know where that is now's the time to find out.

The technical fix is that query() is the wrong method to run on a statement handle. Instead you call execute():

$sth = $pdo->prepare("SELECT odds1 FROM odds WHERE :team1=team1");
$sth->bindParam(':team1', $team1);
$sth->execute();

You can actually minimize this:

$sth = $pdo->prepare("SELECT odds1 FROM odds WHERE :team1=team1");
$sth->execute([ ':team1' => $team1 ]);

This is because execute can take an array of parameters.

The order of arguments in SQL is conventionally column=? but you can do this in either order, MySQL's comparison is bi-directional. It'll make your code more conventional if you write your query as:

$sth = $pdo->prepare("SELECT odds1 FROM odds WHERE team1=:team1");

Now having a column name like odds1 and team1 is usually a sign that you've violated the Zero, One or Infinity Rule of database normalization. A proper normal form would have a one-to-many relationship between one record and others.