php - Yii2：检查数据库中是否存在 ActiveRecord 模型

Question

如何检查数据库中模型的存在？在 Yii 1 版本中是这样的 User::model()->exist()

Answer 1

在 Yii2 中你可以添加exists()到你的查询链中：

User::find()
    ->where( [ 'id' => 1 ] )
    ->exists(); 

（生成的 SQL 如下所示：SELECT 1 FROM `tbl_user` WHERE `id`=1。）

这是Query->exists()来自 Yii2 的源代码：

/**
 * Returns a value indicating whether the query result contains any row of data.
 * @param Connection $db the database connection used to generate the SQL statement.
 * If this parameter is not given, the `db` application component will be used.
 * @return bool whether the query result contains any row of data.
 */
public function exists($db = null)
{
    if ($this->emulateExecution) {
        return false;
    }
    $command = $this->createCommand($db);
    $params = $command->params;
    $command->setSql($command->db->getQueryBuilder()->selectExists($command->getSql()));
    $command->bindValues($params);
    return (bool) $command->queryScalar();
}

Answer 2

if(Mastersettings::find()->where(['id'=>1,'status'=>1])->exists())
{                    
  //....... Your code Here ......
} 

http://yii2ideas.blogspot.in/2017/06/yii2-database-operations.html