Access can access data in Access/Jet, Microsoft SQL Server, Oracle (Oracle Bone Inscriptions Software Company) or any ODBC compatible database. Skilled software designers and data analysts use it to develop application software, while some unskilled programmers and "advanced users" of non-programmers can use it to develop simple application software. Although it supports some object-oriented (OO) technologies, it has not become a complete object-oriented development tool.
In fact, Access is also the name of another communication program of Microsoft, which wants to compete with ProComm and other similar programs. But afterwards, Microsoft confirmed that it was a failed plan and suspended it. A few years later, they renamed the name database software.
[Edit this paragraph] Overview
Access is a Windows-based desktop relational database management system (RDBMS) introduced by Microsoft Corporation, and it is one of the Office series applications. It provides seven objects for building a database system: tables, queries, forms, reports, pages, macros and modules. Various wizards, generators and templates are provided to standardize data storage, data query, interface design and report generation. It provides convenience for establishing a fully functional database management system, so that ordinary users can complete most data management tasks without writing codes.
Access, a relay mode of switch. Whether a trunk connection can be established between two ports of two switches depends on the combination of these two port modes. There are also common
(general) access
main stem
(Adaptive) Dynamic-Automatic
Dynamic-ideal
[Edit this paragraph] History
Microsoft access version 1.0 was released in June 1992 1 1.
Microsoft specifies that its minimum requirement for the system is Windows 3.0 with 4 megabytes of memory. The recommended system requirements are 6 megabytes of memory and at least 8 megabytes of hard disk space (14 megabytes of hard disk space is recommended). At that time, the software was distributed as 7 1.44 megabytes floppy disks.
This software can effectively handle a large number of records, but the test shows that it will lead to data corruption in some cases. For example, files larger than 700MB often have problems. (It is worth noting that when the 1.0 version was widely used, most hard disks were smaller than 700MB. The user guide of the software points out that outdated device drivers and incorrect configuration may lead to data loss.
The original name of Access is Cirrus. It was developed before Visual Basic, when the window engine was called Ruby. After seeing the prototype of Ruby, Bill Gates decided to jointly develop this component based on Basic as an independent and extensible application with Access. This project is called Thunder. These two projects are independently developed as the underlying window engines and are incompatible with each other. However, after VBA appeared, they were merged.
At the end of 1995, access 95 was released, which is the world's first 32-bit relational database management system, making the application of access popularized and developed continuously.
1997, published by access 97. Its biggest feature is that it begins to support web technology in the access database. The development of this technology has opened up the development of access database from desktop to network.
At the beginning of the 20th century, Microsoft released access2000, which is the sixth generation product of Microsoft's powerful desktop database management system and the third version of 32-bit access. At this point, the popularity of access in the field of desktop relational database has jumped to a new level.
In 2003, Microsoft officially released access 2003, which is the latest version released after 2002. It inherits the advantages of the previous version and adds some functions.
[Edit this paragraph] Purpose
Microsoft Access is widely used in many places, such as small businesses, departments of large companies, and developers who love programming and making desktop systems that process data. It is also often used to develop simple WEB applications. These applications run on the Internet information service by using ASP technology. More complex WEB applications use PHP/MySQL or ASP/Microsoft SQL Server. ..
Its ease of use and powerful design tools provide many functions for junior programmers. However, this ease of use can be misleading. These developers are office workers who have no training in application or data design. So many people think that such developers can create usable systems, but many people think that the limitations of the tools themselves lead to such misleading.
Some professional application developers use Access as a tool for rapid application development, especially for street salesmen to make prototypes or stand-alone applications. However, if you access data through the network, the scalability of access is not high. Therefore, when programs are used by more users, their choices are often some client-server based solutions, such as Oracle, DB2, Microsoft SQL Server, Windows SharePoint Services, PostgreSQL, MySQL, Alpha Five, MaxDB or Filemaker. In any case, many functions of Access (forms, reports, sequences and VB codes) can be used as post-applications of other databases, including JET (file-based database engine, which Access uses by default), Microsoft SQL Server, Oracle and any other ODBC-compatible products. This method allows developers to move the data of mature applications to a more powerful server without sacrificing the development in the appropriate location.
Many developers who use Microsoft Access use Leszynski naming convention, although it is not common; It is a programming conference, not a rule implemented by DBMS.
[Edit this paragraph] function
One advantage is that from the programmer's point of view, there are SQL queries that can be observed and edited as SQL statements, and SQL statements can be directly used in macros and VBA modules to enter tables. Users may mix two VBA programs, and the programming form and logic of "macro" neither provide the possibility of object-oriented.
At that time, the generator of importing and exporting reports could create complex reports for this task, and it was not as full of features and power-crystal report as other popular database report generators. MSDE (Microsoft SQL Server Desktop Engine) 2000 is a pocket version of MSSQL Server 2000, which is included in the development version of Office XP and used as an alternative to enter the JET database engine. As soon as possible * version of MSDE and Microsoft's exchange server actually use this jet engine to process massive data and put a "fake" on the application layer of those applications. Regarding this fact, the lack of knowledge leads to disrespect for software products that enter/exit the home, especially for "big" projects. )
The ability to enter the split and paste function makes it a useful tool for linking other databases (for example, Oracle and Microsoft SQL servers during data or database conversion). Various entrance and exit door functions, as well as points given to windows and other platform applications, can be performed from within the application or manually by the user upon request. For example, a very tight SNP is fully formatted to be shared with people who do not have full access to the software. It can also be easily upgraded to Microsoft SQL server.
Completely different from the general RDBMS, it lacks database triggers and stored procedures. Since MS Access 2000 (Jet 4.0), developers can set parameters in queries, similar to stored procedures, but these "stored procedures" can only handle one procedure. When the data in the table changes, it does allow the form to contain trigger code, which is supported by RDBMS in entering the ordinary process of operation storage through queries and other technologies.
[Edit this paragraph] Development
Input the available programming language, and then in another product, Microsoft office furniture, Microsoft applies Visual Basic. Two COM components of database access information base are provided: the old data access object (DAO) and the new ActiveX data object (Busy).
MicrosoftAccess is easy to apply to small projects, but the scale is not effective. If it is applied to large-scale projects, it will be difficult to design.
All database queries, forms and reports are stored in the database, and keep ideal coordination with related models, and there is no possibility of becoming physical organization classes with them.
One design technique is to allocate incoming applications between data and plans. One database should contain only tables and relationships, while the other database should contain all plans, forms, reports and queries, as well as connections to the first database table. Unfortunately, there is no relevant path to access when linking, so those development environments should have the same path as this production environment (although you can write your own "dynamic linking program", you can always find a file in VBA to search this directory tree, and if it finds this current path, it will not work).
This technology also allows developers to apply it in different files, so some architectures are possible.
Advantages of access
(1) single storage mode
The objects managed by Access include tables, queries, forms, reports, pages, macros and modules. All the above objects are stored in a suffix (.mdb) to facilitate user operation and management.
(2) Object-oriented
Access is an object-oriented development tool, which objectifies various functions in the database system and encapsulates various functions of database management in various objects. It regards an application system as a series of objects. For each object, it defines a set of methods and properties to define the behavior and foreign countries of the object. Users can also extend methods and properties to objects as needed. Through the methods and attributes of objects, the operation and management of the database are completed, which greatly simplifies the development work of users. At the same time, this object-oriented development method makes it easier to develop applications.
(3) friendly interface and simple operation
Access is a visualization tool, but the style is exactly the same as Windows. Users want to generate objects and apply them, just drag them with the mouse, which is very intuitive and convenient. The system also provides table generator, query generator, report designer, database wizard, table wizard, query wizard, form wizard, report wizard and other tools, which are simple to operate and easy to use and master.
(4) Integrated environment, processing all kinds of data and information.
Based on the integrated development environment under Windows operating system, Access integrates various wizards and generator tools, which greatly improves the working efficiency of developers and makes it convenient and orderly to establish databases, create tables, design user interfaces, design data queries and print reports.
(5)Access supports ODBC (Open Database Connection). Using the powerful functions of DDE (Dynamic Data Exchange) and OLE (Object Connection and Embedding) of Access, bitmaps, sounds, Excel tables and Word documents can be embedded in a data table, and dynamic database reports and forms can also be established. Access can also apply programs to the network and connect with dynamic data on the network. Using database to access page objects to generate HTML files makes it easy to build Internet/Intranet applications.
Disadvantages of access
ACCESS is a small database. Since it is small, it has its fundamental limitations. In the following cases, the database will basically be overwhelmed:
The 1. database is too large, and the performance of the general ACCESS database will drop sharply when it reaches about 50M!
2. The website is heavily visited, and there are often about 100 people online.
3. There are too many records. When the number of records reaches about 6.5438+million, the performance will drop sharply!
C function
Function name: access
Function: Determine the access rights of files.
Usage: intaccess (constchar * filename, intamode);
[Edit this paragraph] Visit
abstract
# include & ltio.h & gt
int _access(const char *path，int mode)；
describe
The access function, when used with a file, determines whether the specified file exists and can be accessed as specified by the mode value. When used with directories, _access only determines whether the specified directory exists. Because all directories have read and write permissions under Windows.
The mode parameter can be one of the following:
00 only exists
02 write permission
04 read permission
06 read and write permissions
return
0 if the file has the given schema; -1 if an error occurs.
Portability:
Windows. There are similar functions under Unix.
Note that lcc-win32 accepts both _access (Microsoft Convention) and access.
Program example:
# include & ltstdio.h & gt
# include & ltio.h & gt
int file _ exists(char * filename)；
int main(void)
{
Printf ("does not exist. FIL exists: %s\n ",
file_exists("NOTEXISTS。 FIL”)？ "Yes": "No");
Returns 0;
}
Int file _ exists(char * file name)
{
return (access(filename，0)= = 0)；
}
Access database security mode
I. Password type
Give the database a random and complicated name to avoid being guessed and downloaded. This method was very popular in the past, because everyone had confidence in their own code. However, with the error prompt to reveal the database address and illegally download the database, this method is less and less used.
The second is "#" type.
When a request is made from a URL, # is added to the database name, where # is the character that separates the request address from the request parameter. For example, if you know the database name and request it directly, the WEB server will think that you are requesting access instead of access#. Mdb, so you will be prompted that the file cannot be found. Unfortunately, these special characters will have a special expression in the URL. For example, the special expression of # is %23. Also, if you use a download tool such as FlashGet, you can download it directly.
Third, ASP style.
This practice is very professional but also very safe, and it is very popular now, but now many people only do half of it, just change the data name to ASP, so that they can download the database directly with download tools such as FlashGet. The correct approach is to take two steps:
Step 1: Create a field with any name in the database, the type is OLE object, and the content is set to single byte. "
After this code runs, a nodownload table will be generated in the database, and the field in the table is not down. If a data table with the same name already exists in the database, please change the nodownload in the code to the name of the required data table.
Fourth, asa style.
The essence of this method is to use IIS to protect ASA files, so that database files cannot be downloaded directly from URL, but this method is misunderstood as just changing the file suffix to ASA. You should know that IIS only requests protection for the file name global.asa, so this method can only set the database name to global.asa, and it should be noted that it is best not to put it in the root directory or virtual directory of the host after setting it to global.asa, otherwise it will be tried by the normal global.asa file of IIS.
A new mode of information exchange in OpenAccess
Open access is a new academic information dissemination and publishing mode developed under the network environment. Its rise has had a great impact on the way of information exchange and utilization, and it has been widely concerned by international academic circles, publishing circles and library academic circles.
Open access is usually translated into open access and open access. The translation of "open access" in this paper is mainly based on two considerations. First, compared with acquisition, "access" includes not only the acquisition of users, but also the storage of authors, so the use of "access" can cover the connotation of OA more comprehensively; Secondly, in the fields of library science and information science, it has become a habit to translate the word access into "access".
At present, the widely accepted definition of OA comes from the Budapest Open Access Initiative (BOAI), that is, OA means that users can read, download, copy, disseminate, print and retrieve the full text of a paper for free through the public Internet, or link the full text of the paper, index the paper, compile the paper into software, or use the paper for any other legal purpose, whether economic or legal. The only constraint on reproduction and dissemination, and the only function of copyright here, is to ensure that the author has the right to protect the integrity of his works, and ask others to express their gratitude and indicate the source when using the author's works in an appropriate way.
An important force to promote the open access movement
Open access meets the motivation and utilization needs of authors and readers for non-profit information dissemination. In recent years, it has developed vigorously, and the main driving forces are: ① government departments and research funding institutions. On the one hand, it promotes the open access movement through policies. In recent years, some governments and research funding institutions in Europe and America have actively advocated that scientific research results supported by public investment should be used and enjoyed free of charge by the whole society and guaranteed by formulating policies. For example, the National Institutes of Health (NIH) is the largest medical research funding unit in the world, and it has a public access policy. On the other hand, it provides financial support. With the development of the open access movement, more and more government departments, research funding institutions and foundations are willing to provide financial support for the open access of scientific research results. ② Academic researchers. Researchers are creators, reviewers and consumers of scientific research results. At present, academic publishing is monopolized by commercial publishing houses, but academic researchers, as creators of scientific research results, are not free to enjoy scientific research results. Therefore, scientists strongly call for the initiative and control of academic publishing to be taken back to researchers. ③ University. Universities are important practitioners and supporters of the open access movement. In recent years, some well-known universities have launched institutional storage, such as University of California, Massachusetts Institute of Technology, Harvard University and Stanford University, etc., to preserve the research results of faculty and staff according to the requirements of the school's open access policy, open them to the public for free, and provide them on the Internet. ④ Library. The library community is an active participant in the open access movement. By establishing an alliance to promote the open access movement, vigorously promoting open resources on the website, and establishing an institutional library, we are committed to promoting and creating an academic exchange system based on the network environment serving scientific research. ⑤ Internet. From a technical point of view, an important driving force of open access is the Internet. The application of computer and network technology in publishing field reduces the total cost of online publishing and online communication, and makes open access an effective and feasible academic publishing and communication mode.
The main impact of open access
Open access is a change in the way of academic communication. Open access literature is digital, online, free and almost free from copyright and authorization restrictions, so everyone in the world has the opportunity to contact and enjoy research results, thus accelerating the dissemination of academic information, promoting the rapid development of scientific research and enhancing the public use of scientific research. It has different degrees of influence on readers, authors, research institutions, libraries and publishing units.
(1) For the author, it has expanded the readership, expanded the dissemination scope of academic achievements, increased the opportunities for academic achievements to participate in exchanges and be cited, and improved the influence and exhibition power of the achievements. (2) For readers, it is convenient and quick to obtain the research results of peers for free, without facing the dispute of fair use or the fear of possible infringement, and at the same time, it also improves the timeliness of obtaining information. (3) For research institutions, on the one hand, with the wide spread of academic achievements, the scientific research strength of the institutions is prominent and their popularity is improved. On the other hand, as users of academic achievements, we should reduce expenses and avoid repeated payment for publishing and obtaining academic achievements. (4) For funding institutions, the research work funded by them is more open and influential, and the scientific research results are more widely disseminated, which makes the investment generate greater social benefits. ⑤ For the library, it has alleviated the shortage of funds to some extent, collected and sorted out the open access resources on the Internet, expanded the digital collection, and enhanced the information guarantee ability of the library. In addition, it also diverts library users and weakens the role of library information intermediary. Open access is a challenge for publishers. On the one hand, it expands the utilization rate and influence of periodical papers, and its direct effect is to increase the cited frequency of papers; On the other hand, it affects the circulation and high-quality manuscript sources to a certain extent, reduces profits and reduces market share.
Main problems in open access
Although the open access movement is booming, it is still immature in terms of operating expenses, quality control and intellectual property rights. (1) Operating expenses. The operation of open access periodicals and open access warehouses requires costs, including peer review fees, hardware investment, resource maintenance, etc. At present, a reasonable and effective financial support model has not been established, which mainly includes author payment, scientific research institution payment and various subsidies, and the economic operation mechanism is the core issue. ② Intellectual property protection. As a network publishing mode, what are the manifestations of intellectual property rights, how to formulate corresponding management strategies, how to protect the interests of property owners, how to control the balance of rights between readers and authors and other issues need to be solved urgently. ③ Quality control. Open access warehousing should lack peer review, that is to say, there is no objective way to measure the quality of papers, and readers can only evaluate the content themselves, which may benefit those who are already at the top of the knowledge system. For example, the open access website of Harvard University may attract readers because of its world-class reputation, while the papers published by an unknown school or unknown scholar in developing countries may attract less attention. How to formulate quality control strategies, especially how to establish an effective and cross-institutional evaluation alliance system is particularly important. (4) Technical problems. Applying advanced technology to open access will help users get free resources better. Therefore, how to establish a global federal information organization and service architecture and a dynamic digital object management system is an important guarantee for the sustainable development of open access.
As a new mode of academic publishing and information exchange, open access is essentially a free, equal, fair and barrier-free access to academic information. With the vigorous development of open access movement, there are more and more open access resources, and their quantity, quality and academic influence are increasing day by day. Solutions to related problems are also constantly explored and studied in practice. With the increasing publicity of the concept of "knowledge sharing is power", the Open Access Games has attracted more and more attention and support. [