Microsoft Access
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| Microsoft Office Access | |
|---|---|
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 Office Access 2007 running on Microsoft Windows Vista. |
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| Developed by | Microsoft |
| Latest release | 12.0.6211.1000 (2007 SP1) / December 11, 2007 |
| OS | Microsoft Windows |
| Genre | RDBMS |
| License | Proprietary EULA |
| Website | Microsoft Office Access Homepage |
Microsoft Office Access, previously known as Microsoft Access, is a relational database management system from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software development tools. It is a member of the 2007 Microsoft Office system.
Access can use data stored in Access/Jet, Microsoft SQL Server, Oracle, or any ODBC-compliant data container (including MySQL and PostgreSQL). Skilled software developers and data architects use it to develop application software. Relatively unskilled programmers and non-programmer "power users" can use it to build simple applications. It supports some object-oriented techniques but falls short of being a fully object-oriented development tool.
Access was also the name of a communications program from Microsoft, meant to compete with ProComm and other programs. This proved a failure and was dropped.[1] Years later Microsoft reused the name for its database software.
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[edit] History
Access version 1.0 was released in November 1992, followed in May of 1993 by an Access 1.1 release to improve compatibility with other Microsoft products.
Microsoft specified the minimum operating system for Version 2.0 as Microsoft Windows v3.0 with 4 MB of RAM. 6 MB RAM was recommended along with a minimum of 8 MB of available hard disk space (14 MB hard disk space recommended). The product was shipped on seven 1.44 MB diskettes. The manual shows a 1993 copyright date.
The software worked well with very large records sets but testing showed some circumstances caused data corruption. For example, file sizes over 700 MB were problematic (note that most hard disks were smaller than 700 MB at the time this was in wide use). The Getting Started manual warns about a number of circumstances where obsolete device drivers or incorrect configurations can cause data loss.
Access's initial codename was Cirrus; the forms engine was called Ruby. This was before Visual Basic - Bill Gates saw the prototypes and decided that the BASIC language component should be co-developed as a separate expandable application, a project called Thunder. The two projects were developed separately as the underlying forms engines were incompatible with each other; however, these were merged together again after VBA.
[edit] Uses
Access is used by small businesses, within departments of large corporations, and by hobby programmers to create ad hoc customized desktop systems for handling the creation and manipulation of data. Access can be used as a database for basic web based applications hosted on Microsoft's Internet Information Services and utilizing Microsoft Active Server Pages ASP.
Some professional application developers use Access for rapid application development, especially for the creation of prototypes and standalone applications that serve as tools for on-the-road salesmen. Access does not scale well if data access is via a network, so applications that are used by more than a handful of people tend to rely on Client-Server based solutions.[citation needed] However, an Access "front end" (the forms, reports, queries and VB code) can be used against a host of database backends, including JET (file-based database engine, used in Access by default), Microsoft SQL Server, Oracle, and any other ODBC-compliant product.
[edit] Features
One of the benefits of Access from a programmer's perspective is its relative compatibility with SQL (structured query language) —queries may be viewed and edited as SQL statements, and SQL statements can be used directly in Macros and VBA Modules to manipulate Access tables. Users may mix and use both VBA and "Macros" for programming forms and logic and offers object-oriented possibilities.
MSDE (Microsoft SQL Server Desktop Engine) 2000, a mini-version of Microsoft SQL Server 2000, is included with the developer edition of Office XP and may be used with Access as an alternative to the Jet Database Engine.
Unlike a modern RDBMS, the Jet Engine implements database triggers and stored procedures in a non-standard way. Stored Procedures are implemented in VBA, and Triggers are only available from embedded Forms. Both Triggers and Stored procedures are only available to applications built completely within the Access database management system. Client applications built with VB or C++ are not able to access these features. Starting in Access 2000 (Jet 4.0), there is a new syntax for creating queries with parameters, in a way that looks like creating stored procedures, but these procedures are still limited to one statement per procedure.[1] Microsoft Access does allow forms to contain code that is triggered as changes are made to the underlying table (as long as the modifications are done only with that form), and it is common to use pass-through queries and other techniques in Access to run stored procedures in RDBMSs that support these.[[2]]
In ADP files (supported in Access 2000 and later), the database-related features are entirely different, because this type of file connects to a MSDE or Microsoft SQL Server, instead of using the Jet Engine. Thus, it supports the creation of nearly all objects in the underlying server (tables with constraints and triggers, views, stored procedures and UDF-s). However, only forms, reports, macros and modules are stored in the ADP file (the other objects are stored in the back-end database).
[edit] Development
Access allows relatively quick development because all database tables, queries, forms, and reports are stored in the database. For query development, Access utilizes the Query Design Grid, a graphical user interface that allows users to create queries without knowledge of the SQL programming language. In the Query Design Grid, users can "show" the source tables of the query and select the fields they want returned by clicking and dragging them into the grid. Joins can be created by clicking and dragging fields in tables to fields in other tables. Access allows users to view and manipulate the SQL code if desired.
The programming language available in Access is, as in other products of the Microsoft Office suite, Microsoft Visual Basic for Applications. Two database access libraries of COM components are provided: the legacy Data Access Objects (DAO), which was superseded for a time (but still accessible) by ActiveX Data Objects (ADO); however (DAO) has been reintroduced in the latest version, Microsoft Access 2007.
Many developers who use Access use the Leszynski naming convention, though this is not universal; it is a programming convention, not a DBMS-enforced rule.[2] Except in VBA, it is also made redundant by the fact that Access categorises each object automatically and always shows the object type, by prefixing Table: or Query: before the object name when referencing a list of different database objects.
Microsoft Access can be applied to small projects but scales poorly to larger projects involving multiple concurrent users because it is a desktop application, not a true client-server database. When a Microsoft Access database is shared by multiple concurrent users, processing speed suffers. The effect is dramatic when there are more than a few users or if the processing demands of any of the users are high. Access includes an Upsizing Wizard that allows users to upsize their database to Microsoft SQL Server if they want to move to a true client-server database. It is recommended to use Access Data Projects for most situations.
Since all database queries, forms, and reports are stored in the database, and in keeping with the ideals of the relational model, there is no possibility of making a physically structured hierarchy with them.
One recommended technique is to migrate to SQL Server and utilize Access Data Projects. This allows stored procedures, views, and constraints - which are greatly superior to anything found in Jet. Additionally this full client-server design significantly reduces corruption, maintenance and many performance problems.
Access allows no relative paths when linking, so the development environment should have the same path as the production environment (though it is possible to write a "dynamic-linker" routine in VBA that can search out a certain back-end file by searching through the directory tree, if it can't find it in the current path). This technique also allows the developer to divide the application among different files, so some structure is possible.
[edit] Protection
If the database design needs to be secured to prevent from changes, Access databases can be locked/protected (and the source code compiled) by converting the database to an .MDE file. All changes to the database structure (tables, forms, macros, etc.) need to be made to the original MDB and then reconverted to MDE.
Some tools are available for unlocking and 'decompiling', although certain elements including original VBA comments and formatting are normally irretrievable.
[edit] File extensions
Microsoft Access saves information under the following file formats:
| File format | Extension |
|---|---|
| Access Project | .adp |
| Access Blank Project Template | .adn |
| Access Database (2007) | .accdb |
| Access Database (2003 and earlier) | .mdb |
| Access Database, used for addins (2,95,97), previously used for workgroups (2). | .mda |
| Access Workgroup, database for user-level security. | .mdw |
| Access (SQL Server) detached database (2000) | .mdf |
| Protected Access Database, with compiled VBA (2003 and earlier) | .mde |
| Protected Access Database, with compiled VBA (2007) | .accde |
| Windows Shortcut: Access Macro | .mam |
| Windows Shortcut: Access Query | .maq |
| Windows Shortcut: Access Report | .mar |
| Windows Shortcut: Access Table | .mat |
| Windows Shortcut: Access Form | .maf |
[edit] Versions
| Date | Version | Version number |
Supported OS | Office suite version |
|---|---|---|---|---|
| 1992 | Access 1.1 |
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Windows 3.1x | |
| 1993 | Access 2.0 |
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Windows 3.1x | Office 4.3 Pro |
| 1995 | Access for Windows 95 |
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Windows 95 | Office 95 Professional |
| 1997 | Access 97 |
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Windows 9x, NT 3.5/4.0 | Office 97 Professional and Developer |
| 1999 | Access 2000 |
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Windows 9x, NT 4.0, 2000 | Office 2000 Professional, Premium and Developer |
| 2001 | Access 2002 |
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Windows 98, Me, 2000, XP | Office XP Professional and Developer |
| 2003 | Access 2003 |
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Windows 2000, XP | Office 2003 Professional and Professional Enterprise |
| 2007 | Microsoft Office Access 2007 |
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Windows XP SP2, Vista | Office 2007 Professional, Professional Plus, Ultimate and Enterprise |
There are no Access 3.0 to 6.0 because the Windows 95 version was launched with Word 7. All of the Office 95 products have OLE 2 capabilities, and Access 7 shows that it was compatible with Word 7.
[edit] Competing software
- Amiga Datastore
- Alpha Five
- Borland Paradox
- Datawasp
- dBase
- FileMaker Pro (formerly Claris Filemaker)
- Kexi
- Lotus Approach
- NeoOffice
- OpenOffice.org Base
- Oracle XE
- Sun StarBase
- SQLite
- Sybase PowerBuilder
- MySQL
- PostgreSQL
- Omnis Studio
[edit] Database protection
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This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
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[edit] External links
- Microsoft Access Home Page
- Microsoft Access Newsgroups
- A FAQ site about Microsoft Access
- Microsoft Access for Beginners
