php - 如果表中不存在 userID，则添加 mysql 行

Question

我正在向此代码发送发布请求:

$name = (string)$_POST['name'];
$id = (int)$_POST['id'];

$query = "INSERT INTO Users (name, userID) VALUES ('$name', '$id')";


$result = mysqli_query($link,$query);

效果很好，它会向表中添加一行。我如何检查以下行之一中是否已准备好用户ID？

Answer 1

这样做

$query = "SELECT COUNT(*) FROM Users WHERE userID = '$id'";

$result = mysqli_query($link,$query);

if ( mysqli_fetch_assoc($result) ) {
    $message = "Already exists";
} else {
    $query = "INSERT INTO Users (name, userID) VALUES ('$name', '$id')";
    $result = mysqli_query($link,$query);
}