When attempting to attach database files from another SQL Server instance, you'll encounter Error 15023 (Cannot attach a database with the same name) if the database name conflicts with an existing database. This commonly occurs when dealing with system databases like msdb or when restoring backups from similar environments.

Here are three reliable approaches to resolve this issue:

Method 1: Using T-SQL with FOR ATTACH_REBUILD_LOG

CREATE DATABASE [RecoveredDB] ON 
( FILENAME = N'C:\temp\msdbdata.mdf' ),
( FILENAME = N'C:\temp\msdblog.ldf' )
FOR ATTACH_REBUILD_LOG;

This method creates a new database name while attaching the existing files. The REBUILD_LOG option handles cases where the log file might be corrupted.

Method 2: Detaching the Original Database First

-- If you can afford to temporarily remove the existing database
USE master;
GO
EXEC sp_detach_db 'msdb';
GO

-- Now attach the recovered database with original name
CREATE DATABASE [msdb] ON 
( FILENAME = N'C:\temp\msdbdata.mdf' ),
( FILENAME = N'C:\temp\msdblog.ldf' )
FOR ATTACH;
GO

Method 3: Using sp_attach_single_file_db (For Special Cases)

-- When you only have the MDF file
EXEC sp_attach_single_file_db @dbname = 'RecoveredDB',
@physname = 'C:\temp\msdbdata.mdf';

For cases where you need to preserve the original name but can't detach the existing database, you can modify the database metadata before attachment:

-- Create a dummy database
CREATE DATABASE temp_attach;
GO

-- Take it offline to manipulate files
ALTER DATABASE temp_attach SET OFFLINE;
GO

-- Replace the physical files (manually copy your MDF/LDF files 
-- to the dummy database's file locations)

-- Bring it back online with new content
ALTER DATABASE temp_attach SET ONLINE;
GO

• Always make backup copies of your MDF/LDF files before attempting attachment
• File permissions must allow SQL Server service account to access the files
• Version compatibility matters - you can't attach a newer version database to an older SQL Server
• For system databases, additional steps may be required after attachment

Here's a script to handle multiple database attachments with name conflicts:

$sqlInstance = "YourServer\Instance"
$filePairs = @{
    "OldDB1" = @("C:\temp\db1.mdf", "C:\temp\db1_log.ldf")
    "OldDB2" = @("C:\temp\db2.mdf", "C:\temp\db2_log.ldf")
}

foreach ($db in $filePairs.Keys) {
    $newName = "Recovered_" + $db
    $mdf = $filePairs[$db][0]
    $ldf = $filePairs[$db][1]
    
    $sql = "CREATE DATABASE [$newName] ON (FILENAME = N'$mdf'), (FILENAME = N'$ldf') FOR ATTACH_REBUILD_LOG;"
    Invoke-Sqlcmd -ServerInstance $sqlInstance -Query $sql
}

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When attempting to attach MDF/LDF files from another SQL Server instance, you might encounter this common error:

Cannot attach a database with the same name as an existing database. (Microsoft.SqlServer.Smo)

This occurs when the database name in the MDF file conflicts with an existing database in your current SQL Server instance.

Here are three reliable methods to resolve this issue:

Method 1: Using T-SQL with FOR ATTACH_REBUILD_LOG

This approach lets you attach the database while specifying a new name:

CREATE DATABASE [RecoveredDB] ON 
    (FILENAME = 'C:\temp\msdbdata.mdf'),
    (FILENAME = 'C:\temp\msdbdata_log.ldf')
FOR ATTACH_REBUILD_LOG;
GO

Key points:

• ATTACH_REBUILD_LOG regenerates the transaction log if needed
• Works even if the original SQL Server version was different
• May need to specify the full file paths

Method 2: Detaching First (When Possible)

If you have access to both systems temporarily:

-- On original server:
USE master;
GO
ALTER DATABASE [msdbdata] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
GO
EXEC sp_detach_db 'msdbdata', 'true';
GO

-- On new server after file transfer:
CREATE DATABASE [NewDBName] ON 
    (FILENAME = 'C:\new_location\msdbdata.mdf'),
    (FILENAME = 'C:\new_location\msdbdata_log.ldf')
FOR ATTACH;
GO

Method 3: Using SQL Server Management Studio (GUI)

For those preferring visual tools:

1. Right-click "Databases" in Object Explorer
2. Select "Attach"
3. Click "Add" and browse to your MDF file
4. Before clicking OK, change the "Attach As" name
5. Verify the LDF path is correct

For more complex situations:

Handsing Orphaned Users

After attachment, you might need to fix user mappings:

USE [RecoveredDB];
GO
EXEC sp_change_users_login 'Auto_Fix', 'username';
GO

Version Compatibility Issues

If the files came from a newer SQL Server version:

-- Check compatibility level
SELECT name, compatibility_level FROM sys.databases;

-- Change compatibility level if needed
ALTER DATABASE [RecoveredDB] SET COMPATIBILITY_LEVEL = 150;
GO

• Always work on copies of your MDF/LDF files
• Check file permissions before attaching
• Consider using DBCC CHECKDB after attachment
• For production systems, test in development first