Error Attach file SQL: An error occurred when attaching the database(s). Click the hyperlink in the Message column for details.

Try this one

Step 1 Right-click “Databases” and click the “Attach” option to open the Attach Databases dialog box.

Step 2 Click the “Add” button to open the Locate Database Files dialog box.

Step 3 Type in the full name of the .MDF file, including the full device and directory path, as the following example illustrates: c:\StudentsDB.mdf Click the "OK" button. SQL Server Management Studio loads the database from the .MDF file.

OR

Step 1 Click “New Query” in the Management Studio’s main toolbar.

Step 2 Type a Create Database statement using the following Transact-SQL code: CREATE DATABASE MyDatabase ON (FILENAME = 'c:\StudentsDB.mdf'), (FILENAME = ' c:\StudentsDB.ldf') FOR ATTACH;

Step 3 Click the “Execute” button in the Transact-SQL toolbar. SQL Server Management Studio restores the database.

OR

CREATE DATABASE StudentDB ON
(FILENAME = N'C:\StudentsDB.mdf')
FOR ATTACH_REBUILD_LOG
GO

Nếu báo lỗi không truy xuất được file mdf hoặc ldf trong thư mục, 
hãy vào thư mục, 
chọn Properties, 
sau đó qua phần permistion, 
click từng user và chọn hết quyền truy xuất. 
Sau đó nhấn OK và run lại dòng Query.

create database AP09 on (filename = 'F:\Asia\Tuan2\AP09\Data\Asia2009s.mdf'),
(filename = 'F:\Asia\Tuan2\AP09\Data\Asia2009s.ldf') for attach
go