Physical View In a well design database, not only should the database be
easy to share and change with many different users, but the database should also
provide different logical and physical views for users under different purpose.
Definition of Physical View The word physical view comes from the viewing of the
database. The viewing of database can be categorized into two categories:
physical view and logical view. In viewing a database, there can be many
different ways users can view a database depending on their needs and purposes.
Physical view refers to the way data are physically stored and processed in a
database. On the other side, logical view is designed to suit the need of
different users by representing data in a meaningful format. Another word, the logical view tells the users,
in their term, what is in the database. So while there can be numerous logical
views of a database to suit the needs of the users, there can only be one
physical view of a database because physical view deals with the physical
storage of information on a storage device. Benefit of Different View The capability of allowing different views (both logical
views and physical views) in a database, gives users a lot of flexibility. With
the logical views, the users can see data differently from how they are stored
and most of all, users doesn’t need to know the technically detail of the
physical storage. On the other hand, database specialist and advance users
could benefit from the use of physical view of the database because through
physical view, they can see the physical storage of the data. This allows
specialist to make the database more efficient. Understanding the purpose of different views and examples: Understanding physical view and the difference between physical and logical views is very important. Imagine that if a database call “datasoft” hit the market with only one physical view, would the database sell and be very popular? Maybe not. This is because the database would get too technical that user has to look through the physical storage to see the database itself. How about if “datasoft” now has one physical view and one logical view, would the database sell and be popular? Maybe not, because there’s only one way the users the view the database no matter how many users are there. Think about the employee database in a restaurant, it would stores lots of data like employee id, social security id, numbers of complaints, hours worked, hourly rate, vacation time, sick days taken, taxes paid and wage paid. However, managers and employees doesn’t need to see all the information of that database. For employee, the data that are relevant to them are hour work and hourly rate, but they do not need to see data like numbers of complaints. For managers, data like numbers of complaints, hours work and wage paid would be necessary for them to monitor the cost and access employee performance. However, managers do not need see the data like social security as those are personal information of the employee. Hence, a database would works best when it has many different logical views for different users and each view would have only the relevant information for that users. The physical view of the database becomes useful when a database specialist design the database and makes the database efficient. The physical views contain the information of where the data are physically stored. In the example of the restaurant employee database, the whereabouts of physical storage of the database are irrelevant to manager and employee because they do not need to know that. However, when the database becomes substantially large and complicated, it’s important for database specialist to design the physical storage of the data so that data are well organize and efficient to access. For example, if a database specialist tries to makes the large employee database of the State of California more efficient, he would have to see the physical view of the data to see where the data are stored and whether the data are scattered in different storage or one area. After database specialist analyzes the physical storage of the data using the physical view, then the database specialist would be able to make suggestion to improve the database efficient such as moving data onto different high speed storage devices to make accessing the data more efficient.  Wikipedia LINK Also see Logical View |