What is the pattern that reflects users’ data requirements in database design?

The mode in database design that reflects the user's data requirements is the "external mode". The three-level schema of the database system is the conceptual schema, the external schema and the internal schema; among them, the external schema is also called the user schema, which corresponds to the user level. It is the user's data view and gives each user's local data description. The external schema is the data view of the database seen by one or several users, and is a logical representation of data related to a certain application.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The schema in database design that reflects the user's data requirements is the "external schema".

People have designed a rigorous architecture for the database. The standard structure recognized in the database field is the three-level schema structure, which includes external schema, conceptual schema, and internal schema to effectively organize and manage data. Improved the logical independence and physical independence of the database. The user level corresponds to the external schema, the conceptual level corresponds to the conceptual schema, and the physical level corresponds to the internal schema, allowing users at different levels to form different views of the database.

• Conceptual schema is a description of the global data logical structure in the database system and is a common data view for all users.

• External schema is also called sub-schema or user schema. It is the user's data view and gives a partial data description of each user.

  In a database schema, there are N foreign schemas, and each foreign schema corresponds to a user. Foreign schema ensures the logical independence of data.
  

• #The internal schema is also called the physical schema, which provides the physical storage structure and physical access methods of the database.

  A database has only one internal schema; the internal schema specifies the data storage method, data operation logic, data integrity, data security, and data storage performance.

External mode

External mode is also called submode or user mode, corresponding to the user level. It is a data view of the database seen by one or several users, and is a logical representation of data related to a certain application. The foreign schema is a subset derived from the schema and contains that portion of the data in the schema that is allowed to be used by a specific user. Users can describe and define data records corresponding to users (external schemas) through external schema description languages, and they can also use data manipulation language (Data Manipulation Language, DML) to operate on these data records. The external schema reflects the user's view of the database system.

Conceptual pattern

Conceptual pattern is also called pattern or logical pattern, corresponding to the concept level. It is a global logical structure constructed by the database designer based on a unified point of view, integrating the data of all users. It is an overall description of the logical structure and characteristics of all data in the database, and is a common data view (global view) for all users. It is described and defined by the Data Description Language (DDL) provided by the database management system. Conceptual schema reflects the overall view of the database system.

Internal mode

Internal mode is also called storage mode, which corresponds to the physical level. It is the internal representation or underlying description of all data in the database, and is the lowest level logical description of the database. It describes the storage method and physical structure of the data on the storage medium, and corresponds to the database actually stored on the external storage medium. Internal patterns are described and defined by internal pattern description languages. The internal schema reflects the storage view of the database system.

In a database system, there is only one database. Therefore, as the internal schema that defines and describes the database storage structure and the schema that describes the logical structure of the database, it is also unique, but it is built on the database system. The applications are very extensive and diverse, so the corresponding external model is not unique, nor can it be unique.

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