The main problem solved by the standardization theory of relational database is: how to construct a suitable database logical structure; that is, convert the basic entity-relationship diagram designed in the conceptual structure design stage into one supported by the selected database management system product. The data model conforms to the logical structure.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
The main problem solved by the standardization theory of relational database is: how to construct a suitable logical structure of the database.
The logical structure is independent of any data model. In actual applications, the generally used database environment has been given (such as SQL Server or Oracle or MySql). Since the databases currently used are basically relational databases, it is first necessary to convert the entity-relationship diagram into a relational model, then convert it into a data model supported by the specified database management system according to the characteristics and limitations of the specific database management system, and finally optimize it.
The logical structure design steps of the database
1. Transformation from E-R diagram to relational model
The logical design of the database is mainly to convert the conceptual model into The general relationship model is to transform the entities in the E-R diagram, the attributes of the entities, and the connections between entities into a relationship model. During the conversion process, you will encounter the following problems:
naming problem. For naming issues, you can use the original name, or you can name it differently to avoid duplication of names.
Non-atomic attribute problem. Non-atomic property problems can be expanded vertically and horizontally.
Contact for conversion issues. Contacts can be represented by relationships.
2. Optimization of data model
The result of database logical design is not unique. In order to further improve the performance of the database application system, the structure of the data model should be appropriately modified to increase the query speed.
3. Relational view design
The design of the relational view is also called the external schema design, also called the user schema design, which is a data schema that users can directly access. In the same system, different users can have different relationship views. The relational view comes from the logical schema, but may differ from the logical schema in structure and form, so it is not a simple subset of the logical schema.
The relational view has three main functions:
Provides a certain degree of logical independence for the application by shielding the logical pattern from the external pattern.
Better adapt to the different needs of different users for data.
Delimits different scopes for accessing data for different users, which is conducive to data confidentiality.
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