Yii - 数据访问对象



要执行一个SQL 查询,您应该遵循以下步骤:

  • 创建一个包含 SQL 查询的yii\db\Command
  • 绑定参数(非必需)
  • 执行命令。

步骤 1 - 在 SiteController 中创建一个名为actionTestDb 的函数。

public function actionTestDb(){
   // return a set of rows. each row is an associative array of column names and values.
   // an empty array is returned if the query returned no results
   $users = Yii::$app->db->createCommand('SELECT * FROM user LIMIT 5')
      ->queryAll();
   var_dump($users);
   // return a single row (the first row)
   // false is returned if the query has no result
   $user = Yii::$app->db->createCommand('SELECT * FROM user WHERE id=1')
      ->queryOne();
   var_dump($user);
   // return a single column (the first column)
   // an empty array is returned if the query returned no results
   $userName = Yii::$app->db->createCommand('SELECT name FROM user')
      ->queryColumn();
   var_dump($userName);
   // return a scalar value
   // false is returned if the query has no result
   $count = Yii::$app->db->createCommand('SELECT COUNT(*) FROM user')
      ->queryScalar();
   var_dump($count);
}

上面的例子展示了从数据库中获取数据的各种方法。

步骤 2 - 访问地址https://127.0.0.1:8080/index.php?r=site/test-db,您将看到以下输出。

Create actionTestDb Output

创建 SQL 命令

要创建带有参数的 SQL 命令,您应该始终使用绑定参数的方法来防止 SQL 注入。

步骤 1 - 修改actionTestDb 方法如下。

public function actionTestDb() {
   $firstUser = Yii::$app->db->createCommand('SELECT * FROM user WHERE id = :id')
      ->bindValue(':id', 1)
      ->queryOne();
   var_dump($firstUser);
   $params = [':id' => 2, ':name' => 'User2'];
   $secondUser = Yii::$app->db->createCommand('SELECT * FROM user WHERE
      id = :id AND name = :name')
      ->bindValues($params)
      ->queryOne();
   var_dump($secondUser);
      //another approach
   $params = [':id' => 3, ':name' => 'User3'];
   $thirdUser = Yii::$app->db->createCommand('SELECT * FROM user WHERE
      id = :id AND name = :name', $params)
      ->queryOne();
   var_dump($thirdUser);
}

在上面的代码中:

  • bindValue() - 绑定单个参数值。

  • bindValues() - 绑定多个参数值。

步骤 2 - 如果您访问地址https://127.0.0.1:8080/index.php?r=site/test-db,您将看到以下输出。

Modified actionTestDb Output

INSERT、UPDATE 和 DELETE 查询

对于 INSERT、UPDATE 和 DELETE 查询,您可以调用 insert()、update() 和 delete() 方法。

步骤 1 - 修改actionTestDb 方法如下。

public function actionTestDb() {
   public function actionTestDb(){
      // INSERT (table name, column values)
      Yii::$app->db->createCommand()->insert('user', [
         'name' => 'My New User',
         'email' => 'mynewuser@gmail.com',
      ])->execute();
      $user = Yii::$app->db->createCommand('SELECT * FROM user WHERE name = :name')
         ->bindValue(':name', 'My New User')
         ->queryOne();
      var_dump($user);
      // UPDATE (table name, column values, condition)
      Yii::$app->db->createCommand()->update('user', ['name' => 'My New User
         Updated'], 'name = "My New User"')->execute();
      $user = Yii::$app->db->createCommand('SELECT * FROM user WHERE name = :name')
         ->bindValue(':name', 'My New User Updated')
         ->queryOne();
      var_dump($user);
      // DELETE (table name, condition)
      Yii::$app->db->createCommand()->delete('user', 'name = "My New User
         Updated"')->execute();
      $user = Yii::$app->db->createCommand('SELECT * FROM user WHERE name = :name')
         ->bindValue(':name', 'My New User Updated')
         ->queryOne();
      var_dump($user);
   }
}

步骤 2 - 在网页浏览器的地址栏中输入 URL https://127.0.0.1:8080/index.php?r=site/test-db,您将看到以下输出。

Insert Update Delete Queries Example
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