UPDATE如果存在，则插入

Question

UPDATE的正确格式是什么，如果存在，则在这种情况下插入 - 我已经设法进行更新并单独插入但需要它们一起？

我想要的是 - 如果日期存在则会更新到全天，如果它不存在则会插入带有新详细信息的新行。

$date = (isset($_POST['date']) ? $_POST['date'] : null);
$reservationType = (isset($_POST['reservation-type']) ? $_POST['reservation-type'] : null);

$connect = new mysqli($servername, $username, $password, $dbname);


// check connection 

if ($connect->connect_error) {
    die("connection failed: ". $connect->connect_error);
}

$sql = "SELECT * FROM reservations";
$result = $connect->query($sql);

if ($result -> num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        if ($date == $row['date_of_reservation']) {
           "UPDATE reservations SET reservationType = 'FULLDAY' WHERE   date_of_reservation='$date'";
    }
    else {
        "INSERT INTO reservations (date_of_reservation, reservationType) VALUES ('$date', '$reservationType')";
        }
    }
}

Answer 1

来自the manual：

INSERT INTO table (a,b,c) VALUES (1,2,3)
  ON DUPLICATE KEY UPDATE c=c+1;