Simple MDB Merge Tools Compared: Fast Ways to Combine Access Databases

Simple MDB Merge Tools Compared: Fast Ways to Combine Access DatabasesMerging Microsoft Access (.mdb) databases is a common need: consolidating data from multiple departments, combining historical archives, or integrating distributed user edits into a single canonical file. The process may seem straightforward at first — copy tables from one file to another — but real-world datasets introduce schema differences, conflicting primary keys, relationships, linked tables, and attachment or binary fields that complicate matters. This article compares practical tools and approaches for performing a “simple MDB merge,” highlights common pitfalls, and provides step-by-step workflows and tips to help you complete merges quickly and reliably.

Why merging MDB files can be tricky

• Schema mismatches: field name or type differences, differing indexes and constraints.
• Key collisions: overlapping primary key values need resolution to avoid overwriting or constraint violations.
• Referential integrity: parent/child relationships must be preserved; foreign keys often require remapping.
• Linked tables: some tables may point to external data sources (other Access files, SQL Server, SharePoint).
• Attachment/OLE fields and binary data can be large or stored differently between files.
• Access version differences: .mdb (Jet) vs .accdb (ACE) may require conversion steps.

Tools and approaches compared

Below is a concise comparison of available approaches, from native Access features to third-party utilities and scripting techniques.

Recommended tools for different scenarios

• For one-off, small merges with simple schemas: Microsoft Access Export/Import and Append Queries.
• For repeated merges or many files: VBA scripts inside Access or PowerShell scripts to automate.
• For large datasets, normalization, or enterprise integration: SQL Server Import/Export, SSIS, or moving MDBs into a central RDBMS.
• For users who prefer pre-built UIs and conflict resolution: consider reputable third-party MDB merge tools (evaluate on features, security, and reviews).

Quick workflows

Below are practical step-by-step workflows for three common cases.

1) Simple manual merge (small files, matching schema)

1. Open the target Access file.
2. External Data → New Data Source → From Database → Access.
3. Choose “Import tables, queries, forms, reports, macros, and modules into the current database.”
4. Select the source .mdb and pick tables to import.
5. If table names match, Access will append or prompt to rename — use Append Query if necessary: Create → Query Design → choose Append and map fields.
6. Verify data, adjust indexes, and compact/repair the database (Database Tools → Compact and Repair).

When appending, ensure date formats, text lengths, and nullability are compatible to avoid runtime errors.

2) Merge with key collision handling (medium complexity)

1. Identify tables with primary key collisions.
2. Create a new auto-number key in the target (or in the imported data) and add a mapping table that maps old IDs to new IDs.
3. Import child tables; update their foreign key values according to the mapping table (use Update queries).
4. Use transactions in VBA or SQL to ensure atomicity where possible.

3) Automated merges across many files (repeatable)

• Option A: VBA inside a master front-end
  • Write a VBA routine that loops through a folder, opens each .mdb via DAO/ADO, reads table definitions, creates or aligns schemas in the master DB, and appends rows while maintaining ID mappings.
• Option B: PowerShell + OLEDB
  • Use an OLEDB connection string (Jet/ACE) to connect, run SELECT and INSERT statements, and log conflicts. Good for scheduled automation.
• Option C: Python + pyodbc
  • Use pyodbc to connect to each MDB, read schemas, and perform merges with pandas for transformation. This is scalable and script-testable.

Example: Basic VBA snippet to append a table safely

' VBA example (Access) — append all rows from source.mdb.Table1 into current DB Table1 Sub AppendTableFromMDB(sourcePath As String, tableName As String)     Dim dbDest As DAO.Database     Dim dbSource As DAO.Database     Dim rsSource As DAO.Recordset     Dim rsDest As DAO.Recordset     Set dbDest = CurrentDb()     Set dbSource = DBEngine.Workspaces(0).OpenDatabase(sourcePath)     Set rsSource = dbSource.OpenRecordset(tableName, dbOpenForwardOnly)     Set rsDest = dbDest.OpenRecordset(tableName, dbOpenDynaset)     If Not (rsSource.EOF And rsSource.BOF) Then         rsSource.MoveFirst         Do While Not rsSource.EOF             rsDest.AddNew             Dim fld As DAO.Field             For Each fld In rsSource.Fields                 If FieldExists(rsDest, fld.Name) Then                     rsDest(fld.Name).Value = fld.Value                 End If             Next fld             rsDest.Update             rsSource.MoveNext         Loop     End If     rsSource.Close: rsDest.Close     dbSource.Close End Sub Function FieldExists(rs As DAO.Recordset, fieldName As String) As Boolean     On Error Resume Next     Dim v     v = rs.Fields(fieldName).Name     FieldExists = (Err.Number = 0)     Err.Clear End Function 

Handling common issues and tips

• Always back up all MDB files before merging.
• Work on copies; keep original timestamps and provenance if auditability matters.
• Use checksums or row counts before and after to verify success.
• Document ID remapping tables if you renumber keys.
• Compact and repair after large operations to reclaim space.
• If attachments/large binary fields cause errors, consider exporting them separately (filesystem storage) and re-linking.
• When merging from many sources, normalize—create a staging schema to validate and transform data before inserting into production tables.

Security and compatibility notes

• Some third-party tools may require elevation or install drivers; verify source and trustworthiness.
• If automating from server environments, ensure the Jet/ACE OLEDB providers are installed and licensed appropriately.
• Be cautious with databases that contain user-level security (older MDB-based workgroup information files). Preserve or migrate security as needed.

Final recommendations

• For fast, one-off merges with straightforward schemas, use Access’s built-in Import/Append tools.
• For repeatable, multi-file merges implement a scripted solution (VBA, PowerShell, or Python) and maintain mapping logs.
• For enterprise-scale consolidation, move MDB data into a central RDBMS (SQL Server, PostgreSQL) and use ETL tools for controlled merges.

If you want, I can:

• Provide a ready-to-run VBA script tailored to your schema.
• Write a PowerShell or Python script to merge multiple MDBs in a folder.
• Walk through a sample merge with a small example dataset.