Microsoft Access

Microsoft Access is a database management system from Microsoft that combines a relational database engine with a graphical user interface.

What You Can Upload

• .mdb files (Access 97-2003, Jet 3.0/4.0)
• .accdb files (Access 2007+, ACE format)
• Single file or ZIP archive

What You Get Out

DataMeans converts your data into multiple modern formats:

Output	Description
csv/{TableName}.csv	One CSV file per table with all row data
xlsx/{TableName}.xlsx	Excel workbook per table (omitted for tables over 1,048,575 rows, 16,384 columns or 8,000,000 cells - see note below)
xls/{TableName}.xls	Legacy Excel format per table (omitted for tables over 65,535 rows, 256 columns or 150,000 cells - see note below)
json/{TableName}.json	JSON array of records per table
json/{TableName}.jsonl	Newline-delimited JSON (streaming-friendly)
postgres.sql	PostgreSQL CREATE TABLE + INSERT statements
mysql.sql	The same schema and rows, in MySQL dialect
sqlite.sql	The same schema and rows, in SQLite dialect
ansi.sql	The same schema and rows, in portable ANSI SQL
sqlserver.sql	The same schema and rows, in SQL Server (T-SQL) dialect
report.json	Structured conversion report
report.md	Human-readable conversion summary

How to Export / Obtain Files

1. Locate your Access database file (.mdb or .accdb)
2. Close Microsoft Access if the file is open
3. Optionally, compact and repair the database first
4. Upload the file directly or in a ZIP archive

Supported Features

• Full table data extraction
• Access data types: Text, Number, Date/Time, Currency, AutoNumber, Yes/No, Long Text (Memo), OLE Object and Hyperlink
• NULL value handling
• Unicode text (Access 2000 and later)
• Access 97 text in the code page each column names: Cyrillic, Central European, Greek, Japanese and the rest. Where a column names only the Western default, its text is read in the code page of the Database Origin you choose at upload
• Each table's primary key, over one column or several, becomes its primary key in the SQL files, wherever the data satisfies it
• Relationships defined in Access become foreign keys in the SQL files, wherever the data satisfies them; the SQL file lists any it leaves out, and why
• Other relationships between tables are suggested from the data; the ones you confirm on the job page become foreign keys too

Known Limitations

• VBA/Macro code is not extracted
• Forms, reports and queries are not converted
• Encrypted or password-protected databases are not supported
• Attachment and multi-value fields: Access keeps their contents in hidden tables that are not read, so the column holds Access's internal reference number, and the report names those columns
• A column of a data type DataMeans cannot read (not one of Access's own types, as in a file another program wrote) is left out, and the rest of the table is delivered. The table is marked for review, and the upload preview and the report name each column left out and its type. If none of a table's columns can be read, the table comes out empty with that reason, and an upload whose tables are all empty fails with the reasons rather than finishing with nothing
• A relationship over more than one field is not carried over
• Linked tables are not in the file that links to them. A split database's front end converts its own tables, and the report names the back-end file to upload for the rest

Best Practices

1. Compact and repair your database in Access before uploading it
2. Document custom functions and business logic separately
3. Test with a backup copy first
4. Verify record counts match after import

Note on the Excel formats. An .xlsx sheet holds at most 1,048,575 rows of data and 16,384 columns, and a legacy .xls sheet 65,535 rows and 256 columns. Rather than ship a file that looks complete but is silently cut short, DataMeans leaves a table out of any Excel format it does not fit and notes it in the job report. The .xlsx copy is also left out for tables of more than 8,000,000 cells (1,048,575 rows of 12 columns is 12.6 million), which take too long and too much memory to write, and the .xls copy for tables of more than 150,000 cells, which the legacy format takes far too long to write. The CSV, JSON and SQL outputs always contain every row.

Overview

Microsoft Access is a relational database management system integrated into the Microsoft Office suite, designed for desktop and small business applications. It provides a graphical user interface for creating and managing databases without extensive programming knowledge. Access uses proprietary file formats (.mdb and .accdb) backed by the Jet Database Engine and Access Connectivity Engine (ACE), storing tables, indexes, relationships, queries, forms, reports, macros, and VBA modules in single container files. The system supports multi-user access coordinated through lock files and can be accessed via ODBC/OLE DB drivers for external applications.

History and Background

• 1992: Access 1.0 shipped with Jet 1.0 and the original .mdb format.
• 1994: Access 2.0 shipped with Jet 2.0, retaining the 2 KB page size used since Jet 1.0.
• 1995: Access 95 (7.0) became the first 32-bit version, moved to Jet 3.0 with database replication, and replaced Access Basic with VBA.
• 1997: Access 97 (8.0) used Jet 3.5, which revised locking strategies, and added the Hyperlink data type.
• 1999: Access 2000 (9.0) adopted Jet 4.0 (4 KB pages, Unicode storage with compression, record-level locking).
• 2001: Access 2002 (10.0) continued on Jet 4.0, adding PivotTable/PivotChart views and XML import/export.
• 2003: Access 2003 (11.0) added digital signatures and explicit trust prompts for VBA macros.
• 2007: Access 2007 (12.0) introduced the .accdb format and ACE 12.0 with attachments and multi-valued fields.
• 2010: Access 2010 (14.0) added web databases and data macros.
• 2013: Access 2013 (15.0) introduced the app model for web apps.
• 2015: Access 2016 (16.0) shipped with Office 2016, with modernized templates and a larger Show Table dialog.
• 2018: Access 2019 added the Large Number (BigInt) data type and modern chart types.
• 2021: Access 2021 added the Date/Time Extended data type and dark themes.

File Format Specifications

Access databases are stored in single binary files with embedded components.

File Extensions:

• .mdb: Access 1.0-2003 default format (Jet engine)
• .accdb: Access 2007+ format (ACE 12.0+ engine)
• .adp: Access Data Project (SQL Server linked; Access 2000-2010)
• .accde: Execute-only database with VBA source code removed
• .accdr: Runtime version

File Structure:

• Containers: .mdb uses Jet engine; .accdb uses ACE. Both are little-endian, page-based formats with B-tree indexes.
• Page sizes: Jet 1.x-3.x use 2 KB pages; Jet 4.0 and ACE use 4 KB.
• System catalogs: Hidden tables like MSysObjects, MSysRelationships catalog database objects and relationships.
• Concurrency: Lock files (.ldb for MDB, .laccdb for ACCDB) track shared users.
• Limits: Database size up to 2 GB; 255 fields per table; object names up to 64 characters.
• Encryption: MDB passwords use weak XOR/RC4-based obfuscation; ACCDB supports stronger encryption, AES-128 by default since Access 2010.
• Replication: Supported in Jet MDB; not supported in ACCDB.
• Embedded objects: Forms, reports, modules stored in container but separate from table data.

Key Components:

• Jet/ACE Engine: Core database processing
• DAO/ADO: Data access interfaces
• OLE Objects: Embedded files and images
• Security: User-level permissions (MDB only) and database password encryption
• Replication: Multi-user synchronization for MDB

Data Types and Structures

Access supports various data types with specific storage characteristics:

Type	Size	Description	Use Cases
Short Text	Up to 255 chars	Variable-length text strings	Names, addresses
Long Text	Up to 1 GB	Large text content (Memo)	Descriptions, notes
Number	1-16 bytes	Integer and decimal numbers	Quantities, IDs
Large Number	8 bytes	64-bit big integer	Large counters
Currency	8 bytes	Fixed-point decimal (4 places)	Monetary values
AutoNumber	4-16 bytes	Auto-incrementing counter	Primary keys
Date/Time	8 bytes	Date and time values	Timestamps
Date/Time Extended	42 bytes	High-precision datetime	Precise timing
Yes/No	1 byte	Boolean values	Flags, checkboxes
OLE Object	Variable	Embedded objects	Images, documents
Hyperlink	Variable	Web/file links	URLs, paths
Attachment	Variable	Multiple file attachments	Documents, media
Calculated	Variable	Computed expressions	Derived values

Database Objects:

• Tables: Core data storage with rows and columns
• Indexes: B-tree structures for fast lookups
• Relationships: Foreign key constraints and joins
• Queries: Stored SQL statements and views
• Forms: User interface designs
• Reports: Formatted output layouts
• Macros: Automated actions and workflows
• Modules: VBA code for custom functions

Version Differences

Version	Year	Key Features	File Format
Access 95	1995	32-bit, VBA	.mdb (Jet 3.0)
Access 97	1997	Hyperlink data type	.mdb (Jet 3.5)
Access 2000	1999	ADP, data access pages	.mdb (Jet 4.0)
Access 2002	2001	XML, PivotTable views	.mdb (Jet 4.0)
Access 2003	2003	Digital signatures, macro trust	.mdb (Jet 4.0)
Access 2007	2007	Ribbon, attachments	.accdb (ACE 12.0)
Access 2010	2010	Web databases, data macros	.accdb (ACE 14.0)
Access 2013	2013	Web apps; ADP removed	.accdb (ACE 15.0)
Access 2016	2015	Modernized templates	.accdb (ACE 16.0)
Access 2019	2018	Large Number, modern charts	.accdb (ACE 16.0)
Access 2021	2021	Date/Time Extended, dark themes	.accdb (ACE 16.0)

Compatibility Notes:

• .accdb requires Access 2007 or later
• .mdb files (Access 2000-2003 format) still open in current versions but lack ACCDB-only features
• ADP projects require SQL Server; support was removed in Access 2013
• Runtime versions limit development features
• Access web apps were retired from SharePoint Online in 2018

Technical References

• Access specifications: official size, field, and object limits.
• Data types for Access desktop databases: data type storage sizes and properties.
• Which Access file format should I use?: MDB vs ACCDB capability differences.
• Encrypt a database by using a database password: password/encryption behavior across formats.
• MDB Tools format documentation: reverse-engineered Jet/MDB file format internals.