What is an auto-increment ID? How to obtain and use thinkphp?

As a PHP developer, you may have encountered such a problem: how to get the ID of a newly inserted record in a table that uses an auto-increment ID. In ThinkPHP, you can directly call the $model->getLastInsID() method to get this ID. In this article, we'll cover more details and how to use it.

What is an auto-increment ID?

Auto-increment ID is a numerical value that is automatically generated and incremented in the table and is usually used as a unique identifier for each record. Among databases, MySQL is one of the most commonly used databases that uses auto-incrementing IDs.

How to use auto-increment IDs in ThinkPHP

ThinkPHP, as an efficient, flexible and easy-to-use PHP framework, provides a simple method when dealing with auto-increment IDs in the database. Basically, any table that uses auto-incrementing IDs needs to define the primary key as id and set it to auto-increment. In the model class, you need to tell the framework the primary key name and the data table name. For example:

// 定义模型类
class UserModel extends Model
{
    protected $pk = 'id';
    protected $table = 'user';
}

After defining the model class, you can easily call $model->add() to insert records into the database. For example:

// 插入一条新纪录
$userModel = new UserModel;
$data = [
    'username' => 'thinkphp',
    'email' => 'thinkphp@example.com',
    'password' => 'password',
];
$result = $userModel->add($data);

After executing $userModel->add($data), you can use $userModel->getLastInsID() to get the The auto-incrementing ID of the record inserted in the database. For example:

// 获取最后一次插入的自增 ID
$userId = $userModel->getLastInsID();

How to use getLastInsID method in custom SQL?

If you use the $model->getLastInsID() method in your own SQL, you may encounter the following error:

SQLSTATE[HY000]: General error: 2053 获取最后插入ID失败！请检查数据表是否有自增字段！

This is because$model->getLastInsID() The method will query the database for relevant information about the auto-increment ID. In custom SQL, you need to call mysqli_insert_id() and ## respectively. #PDO::lastInsertId() to get the last inserted auto-increment ID. For example:

// 执行添加记录的 SQL
$sql = 'INSERT INTO thinkphp_user (username, email, password) VALUES (?, ?, ?)';
$result = $userModel->execute($sql, [$data['username'], $data['email'], $data['password']]);

// 获取最后一次插入的自增 ID
$lastInsertId = $userModel->getLastInsID();
if (!$lastInsertId) {
    // 如果获取失败，尝试使用 mysqli_insert_id() 或 PDO::lastInsertId()
    $lastInsertId = $userModel->execute('SELECT LAST_INSERT_ID()');
}

Summary

In ThinkPHP, using auto-increment ID allows you to easily assign a unique identifier to each record. Using the

$model->getLastInsID() method, it is very easy to get the last inserted auto-incremented ID, and allows you to further process the data in the database. However, it should be noted that when using this method in custom SQL, you need to call mysqli_insert_id() and PDO::lastInsertId() respectively.

When writing code, it is recommended to carefully understand the concept and usage of auto-increment ID, as well as the basic principles of the database. This knowledge can help you make your business logic more efficient and stable.

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