With regard to the description of the data, it is reasonable to draw the boundary between primary and high school between “understand the description” and “be able to describe”. In a primary school, a teacher, as a rule, does not have the opportunity to go with the students the whole path of database design. Therefore, it makes sense only to “dissect” the structure of a small, well-designed database. In this case, it is possible to consider the concepts of “table”, “key”, “communication”. And, of course, this is a very convenient and pertinent occasion to discuss data types and to focus students on the fact that the type determines the set of valid operations. With 먹튀검증 this is possible now.
It makes no sense to be limited to a single table database. Of course, such bases have a right to exist, but for training purposes they are of little use, since they do not allow demonstrating a number of important concepts.
In high school, you can spend a full cycle of database design, starting with building an infological model. When moving to a datalogical model, tables will appear that will have to be described. At the substantive level, the boundary between the basic and profile levels is determined by the degree of complexity of the database.
On the methodological the degree of individualization of students
When designing a database with students, it is very important not to represent all its parameters in advance known and defined. Even experienced developers return many times to the various stages of design – they refine both the datalogical and infological models. It is entirely possible for educational purposes to “forget” something, then “discover” the imperfection of the model and clarify it. This is much more effective than presenting the finished “perfect” sample right away.
Interaction of clients with a DBMS is carried out by means of requests for data processing. (Note that a client can be either a person a user, or a program that uses a DBMS as part of an information system.)
- According to the relational model, all data is organized into tables and, accordingly, all requests are processed by tables. It is very important to emphasize that the tables are not only at the input, but also at the output of any query. That is, the result of any query is always a table.
- Note that the tables that are the source data of the query, in turn, may be the result of another query.
- In the diagram above, dashed arrows indicate optional input data for the request.
In the diagram above, dashed arrows indicate optional source request data
To consider all further examples, we need a small demo database filled with a minimum of information. For these purposes we take three tables from the database, which served for similar illustrative purposes in the article “Relational databases” 2. Namely, we restrict ourselves to the tables “Teacher”, “Subject” and the table of communication “Teacher – Subject”.