What is a database scheme?

Database scheme is a way to describe the structure and relationships of information that will be used and held in the database. Some schemes are written in a language that can be interpreted using database management software, while others are completely abstract diagrams. The primary elements of the database scheme are entities and tables. The entity is a data model for an object in the database, while the table is a sequence of values ​​or other entities. Like the plan, a well -designed scheme can be used precisely how the database architecture is designed.

Database schemes are sometimes necessary to explicitly show how the file is stored and refers to the rest of the database. The entity is a representation of the data collection. Like any data structure, it can have a number of fields. However, entities usually have a unique identification field. This is called the primary key.

The primary key is a link to the table. The key must be between all the uniquely udental elements in the table. An example would be the customer number fora database that monitors storage purchases. Each entity can only have one primary key.

entities can also have any number of foreign keys. The foreign key is most often the primary key of another entity in another table. In the above example, a foreign key could be an order number for this customer.

In relational databases, primary and foreign keys are used to express a very important concept of relationships between individual people. In a given example, the customer can have many different orders and orders numbers. The opposite is not true because the order can only have one customer. Relationships about one place are part of the reason that a database scheme is required.

Another type of relationship is called many to them. This is an instance in which an entity cannot only have many relationships with one type, but can also be included in many types with a different type. An example of this is how any number canCustomers order the same product. At the same time, the customer can order any number of products. This relationship much to many is common, but requires special data modeling to work within the database scheme.

While there are some standard conventions that are adhered to when creating a database scheme, there are also many ways to represent data models. Exactly as each scheme object is represented in an abstract design, it is at the discretion of the data modeler. In some situations, the DBMS system will be able to accept a database scheme that is written in a specific way and actually implement part of the design automatically.