Existing relational systems differ markedly by the set of relational operations that are implemented. Many systems do not provide operations intersection, union and difference relations.
In conclusion we can say that during the decade of its existence, technology databases on personal computers emerged as a highly developed branch of the common technology database.
It is well known that an important tool for ensuring the independence of the logical data systems are representations of the mechanisms. Range of users of the class Database extends from casual users, or users are able to meet their information needs directly with the database to application developers, designed so that the tools of their development are hidden from the user. Each of the database in one way or another tends to be one of these poles, and some systems combine both options. System-oriented developers have developed tools for building applications. This kind of tools can be found even in the most developed systems of early, but now the presence of a complex of funds intended for the application developer, has become a required component of all the market-leading DBMS software.
It should be noted that the means of generation of application systems solve even the most time-consuming, but only one of the related problems of this problem - automated production of software code produced by the application system. With this approach, putting a programming aspect of the case, it remains outside the focus is another important task - to create the core of the future information system - its database. Unfortunately, none of the widely-used commercial DBMSs do not have any tools to automate the design database. While the first database for personal computers were designed for single users, and it is possible to simplify the functions of the DBMS, at the present time for many advanced database developed online versions of these systems, which have practically do not differ in the functional aspect of the traditional systems. Here we have to deal with a multi-media and solve the associated problems of specific processes in parallel, access control and data integrity protection.
System database, built with massive online database versions, often rightly called distributed database systems. In fact, we are dealing here not with a distributed database with a distributed (network) access to a centralized database.
Such systems are based on hardware and software of different local area networks.
Most DBMS for PC IBM PC can run on widely distributed networks IBM PC Network (IBM Corp.), Novell Network (Novell Inc.) And several others. As part of the software for "personal" database, a considerable number of families of compatible databases running on different models of computers and different operating environments. The developers of DBMS for PC give special attention to the problems of data exchange with other software systems - systems with database systems, "spreadsheet" with the various application systems. It should be noted that the means of communication with external systems on the PC became an integral part of most software products related to data processing.