Yii數據訪問對象


要執行一個SQL查詢,應該遵循以下步驟 -
  • 創建一個 yii\db\Command 的 SQL查詢命令
  • 綁定參數(非必須)
  • 執行命令
第1步 - 創建一個 actionTestDb()方法在 SiteController 控制器中。
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); echo '<hr/>';
   // 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);echo '<hr/>';
   // 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); echo '<hr/>';
   // 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);
}
上述例子演示從一個數據庫中獲取數據的幾種方法。
第2步 - 在瀏覽器打開URL地址: http://localhost:8080/index.php?r=site/test-db ,會看到輸出如下圖所示。
Yii數據訪問對象

創建一個 SQL命令

要創建使用參數的 SQL 命令,應該始終使用綁定參數的方法來防止SQL注入攻擊。
第1步 - 修改 actionTestDb() 方法使用以以下的方式。
public function actionTestDb() {
   $firstUser = Yii::$app->db->createCommand('SELECT * FROM user WHERE id = :id')
      ->bindValue(':id', 1)
      ->queryOne();
   var_dump($firstUser);echo '<hr/>';
   $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);echo '<hr/>';
      //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);
}

在上面的代碼中 - 

  • bindValue() − 綁定單個參數值

  • bindValues() − 綁定多個參數值

第2步 - 在瀏覽器打開URL地址: http://localhost:8080/index.php?r=site/test-db ,會看到輸出如下圖所示。
Yii數據訪問對象

INSERT, UPDATE 和 DELETE 查詢

對於INSERT,UPDATE和DELETE查詢,可調用 insert(), update() 和 delete() 方法。
第1步 - 修改 actionTestDb() 方法並使用以下代碼:
public function actionTestDb() {
      // INSERT (table name, column values)
      Yii::$app->db->createCommand()->insert('user', [
         'name' => 'My New User',
         'email' => '[email protected]',
      ])->execute();
      $user = Yii::$app->db->createCommand('SELECT * FROM user WHERE name = :name')
         ->bindValue(':name', 'My New User')
         ->queryOne();
      var_dump($user);echo '<hr/>';
      // UPDATE (table name, column values, condition)
      Yii::$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($user);echo '<hr/>';
      // DELETE (table name, condition)
      Yii::$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);
}

第2步 - 在瀏覽器打開URL地址:http://localhost:8080/index.php?r=site/test-db,會看到輸出如下圖所示。

Yii數據訪問對象