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如何通过php计算告诉数据库不接受或插入或更新负值。Mysql XAMPP DONOT将负值插入行
考虑这个PHP代码:
<?php include('index2.php'); ?>
<?php include('db.php'); ?>
<?php
$mobile = $_SESSION['mobile'];
$date = date('M-d,Y H:i:s');
$date2 = date('M-d,Y');
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$amount = $_POST['amount'];
$balance = $_POST['balance'];
$balancenow = $balance - $amount;
if ($amount > $balance) {
$sql3 = "UPDATE users SET balance = '$balancenow'
WHERE mobile = '$mobile'";
if ($conn->query($sql3) === TRUE) {
echo '<a href="index2.php"></a>';
} else {
echo "0";
}
} else {
echo '<script language="javascript">';
echo 'alert("You don't have enough coupon balance")';
echo '</script>';
echo '<a href="index2.php"></a>';
}
$conn->close();
?>
现在,在上面的例子中考虑: '量' 是500,并且平衡是250, 其中inturns让我们用计算为:
$balancenow = $balance - $amount;
= 250-500 = -250
现在,在这种情况下,如何告诉数据库不接受负值并给出了其他语句来代替..
任何帮助表示赞赏..
列类型是'signed'还是'unsigned'? – C2486
为什么你不使用php检查它? –
简单使用'if($ balancenow <0) {echo“negative”; } else {echo“positive”//插入数据库;}' – Saty