我正在使用图表,我需要从数据库中获取最后10个数据并将其打印到图表中。好吧,我可以轻松地做到这一点,但是问题是,数据正以另一种方式打印,因此,不是像这样打印,这只是一个例子:1 2 3 4 5,它正在打印5 4 3 2 1我需要它以正常方式打印。这是我的代码:
$id = $_SESSION['userId'];
$dBname = "infosensor";
$conn = mysqli_connect($servername, $dBUsername, $dBPassword, $dBname);
$sql = "SELECT sensor1, sensor2, sensor3, dias FROM `$id` ORDER BY id DESC LIMIT 10;";
$result = mysqli_query($conn, $sql);
$jsonsensor1 = array();
$jsonsensor2 = array();
$jsonsensor3 = array();
$jsonsensorsum = array();
$date = array();
if (mysqli_num_rows($result) > 0)
{
while ($row = mysqli_fetch_assoc($result))
{
$jsonsensor1[] = intval($row['sensor1'] * ($p = pow(10, 2))) / $p;
$jsonsensor2[] = intval($row['sensor2'] * ($p = pow(10, 2))) / $p;
$jsonsensor3[] = intval($row['sensor3'] * ($p = pow(10, 2))) / $p;
$jsonsensorsum[] = intval(($row['sensor1'] + $row['sensor2'] + $row['sensor3']) * ($p = pow(10, 2))) / $p;
//Data
$geral = (date('d/m/y', strtotime(str_replace('.', '-', $row['dias']))));
$date[] = $geral;
//Horario
$horario = (date('H:i:s', strtotime(str_replace('.', '-', $row['dias']))));
$tempo[] = explode(',', $horario);
}
}
$data = [$jsonsensor1,$jsonsensor2,$jsonsensor3,$jsonsensorsum, $date];
echo json_encode($data);
问题出在这里:
$sql = "SELECT sensor1, sensor2, sensor3, dias FROM `$id` ORDER BY id DESC LIMIT 10;";
怎么样:
SELECT sensor1, sensor2, sensor3, dias
FROM (
SELECT sensor1, sensor2, sensor3, dias, id FROM `$id` ORDER BY id DESC LIMIT 10
) t
ORDER BY id
或者,如果您正在运行MySQL 8.0,则可以使用ROW_NUMBER()
:
SELECT sensor1, sensor2, sensor3, dias
FROM (
SELECT sensor1, sensor2, sensor3, dias, id, ROW_NUMBER() OVER(ORDER BY id DESC) rn
FROM `$id`
) t
WHERE rn <= 10
ORDER BY id