Scheme data
Sheduling the scheme given one more way äîêóìåíòèðîâàíèÿ project. Access has a facility of the visual building of the scheme given in window, which so and is identified Scheme given . In he examines, create or change the relationship between table or request.
Sheduling the scheme helps the developer to define, on what fields are bound main tables and as type relationship. Certainly, in request of the table possible to as please. But even though tables BD and are not bound constant relationship with support of wholeness, developer usually for itself don't care draws the scheme and builds the relationship. Really if this allows the facility of the development, that óäîáíåå to keep the graphic description of the structure of the base in most project this will vastly simplify understanding (âñïîìèíàíèå through what that time) of the logic of the work BD. Besides if the question is creation constant relationships between table then for provision of wholeness given advisable to build these relationship between them.
Amongst developer there is as outside making the scheme, so and enemies. In the last case argue this that that itself scheme - simply graph, and except image relationships by default between table, use from it little. Besides, at development complex project, where are present several groups of ten of the tables, scheme is got bulky and enough çàòðàòíîé in plan of time of the formation. In the same way under complex logic of the work, not always turns out to be suitable hard to prescribe the relationship and more so cascade removing/renovations. Sometimes this better do software.
However at refusal of sheduling the scheme data follows to take into account that Access hides from user realization so named secondary êëþ÷åé , which strictly and the relationships under graphic making. Their possible find in corresponding to family, for instance DAO (indexes, object tabledefs). These indexes do not appear in window index tables (in mode of the constructor of the table press the button Indexes ) and have a specific name. The Indexes the speedups of the process of searching for and sequencing data.
Access in the same way hidden realizes most standard triggers - a check to wholeness and cascade renovations/removing. Here is exactly for task of the description (the presentations) mechanism of relatedness data and needs the interface scheme given .
The Ithaca, the main arguments of the sheduling the structured scheme data:
FOR
- Vastly relieves understanding the logic of the work BD to account of the graphic demonstrative presentation of the relationships between table
- Allows to create cascade renovations/removing facility Access (not software)
- Allows to trace wholeness data facility Access (not software)
AGAINST
- In greater project - a significant temporary expenseses on making the relationships between table
- Not always reasonable hard to prescribe relationship sometimes this disturbs realization of the complex logic of the work of exhibit
The author: Admin
