winenax.blogg.se

Any change done would be absorbed by the mapping between the conceptual and internal levels. With Physical independence, you can easily change the physical storage structures or devices with an effect on the conceptual schema. Compared to Logical Independence, it is easy to achieve physical data independence. It allows you to provide a logical description of the database without the need to specify physical structures. Physical data independence helps you to separate conceptual levels from the internal/physical levels. Students(id: int, name: string, login: string, age: integer)Ĭourses(id: int, cname:string, credits:integer)

View 1: Course info(cid:int,cname:string) At the different levels this is how the implementation will look like: Type of Schema The database has 3 levels as shown in the diagram belowĬonsider an Example of a University Database. Physical data independence occurs at the logical interface level.Before we learn Data Independence, a refresher on Database Levels is important.Physical data independence is used to separate conceptual levels from the internal levels.If we do any changes in the storage size of the database system server, then the Conceptual structure of the database will not be affected.Physical data independence can be defined as the capacity to change the internal schema without having to change the conceptual schema.Logical data independence occurs at the user interface level.If we do any changes in the conceptual view of the data, then the user view of the data would not be affected.Logical data independence is used to separate the external level from the conceptual view.Logical data independence refers characteristic of being able to change the conceptual schema without having to change the external schema.There are two types of data independence: 1. Data independence refers characteristic of being able to modify the schema at one level of the database system without altering the schema at the next higher level.Data independence can be explained using the three-schema architecture.