Question

我看不到我做错了什么，请帮忙。我正在学习Select Last_Insert_Id，现在已经呆了几天了。

$result2 = $mysqli1->query("SELECT LAST_INSERT_ID()");

while($row = mysqli_fetch_assoc($result2)) {
    return $row;
}
$last_id = $row;

$sql = "UPDATE bao_admin_table SET Name='$name' WHERE ID = '$last_id' ";

if ( $mysqli1->query($sql)){

    $_SESSION['message'] = 'Registration successful!';
    header("location: success.php"); 

}else{
    $_SESSION['message'] = 'Registration failed!';
    header("location: error2.php");
}

Answer 1

我想您可能正在插入录音，那么只有您可以获取最后插入的ID。有两种方法可以实现它，

插入后获取最后插入的值。这就是您可以做到的方式

$sql = "INSERT INTO MyGuests (firstname, lastname, email) VALUES ('John', 'Doe', 'john@example.com')";
if (mysqli_query($conn, $sql)) 
{
$last_id = mysqli_insert_id($conn);
echo "New record created successfully. Last inserted ID is: " . $last_id;
} 
else 
{
 echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

我希望您拥有至少一个主键来从表中提取唯一记录，因此，这是通过递减顺序获得最后一个id的方法。

`

$sql = "SELECT * FROM MyGuests ORDER BY id DESC";
$result = $conn->query($sql);
if ($result->num_rows > 0) 
{// output data of each row
while($row = $result->fetch_assoc()) 
{
    echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} 
else 
{
echo "0 results";
}

`

Answer 2

您可以通过执行以下操作来获取last_insert_id

 $last_id = $conn->insert_id;

有关更多信息：https://www.w3schools.com/PHP/php_mysql_insert_lastid.asp

或者您也可以这样做

$selectquery="SELECT id FROM tableName ORDER BY id DESC LIMIT 1";
$result = $mysqli->query($selectquery);
$row = $result->fetch_assoc();
$last_id=$row['id'];
echo $last_id;

LAST_INSERT_ID（）无法使此代码正常工作

2 个答案: