Erro ao rodar comando "vendor/bin/doctrine orm:schema-tool:create"

Ao rodar o comando "vendor/bin/doctrine orm:schema-tool:create" dentro o diretório do projeto o terminal retorna o seguinte erro:

!                                                                                                                      
 ! [CAUTION] This operation should not be executed in a production environment!                                         
 !                                                                                                                      

 Creating database schema...


In ToolsException.php line 34:

  Schema-Tool failed with Error 'An exception occurred in driver: SQLSTATE[HY000] [1049] Unknown database 'mydb'' while executing DDL: CREATE TABLE Aluno (id INT AUTO_INCREMENT NOT NULL, nom  
  e VARCHAR(255) NOT NULL, PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE = InnoDB                                                                                  


In AbstractMySQLDriver.php line 93:

  An exception occurred in driver: SQLSTATE[HY000] [1049] Unknown database 'mydb'  


In PDOConnection.php line 31:

  SQLSTATE[HY000] [1049] Unknown database 'mydb'  


In PDOConnection.php line 27:

  SQLSTATE[HY000] [1049] Unknown database 'mydb'  


orm:schema-tool:create [--dump-sql]

Aqui estou usando o MySQL (MariaDB). E no arquivo "EntityManagerFactory.php" configurei a linha da "$connection" dessa forma:

$connection = [            
            'url' => 'mysql://root:@localhost/mydb',
        ];