Database or database final part

ABSTRACT DATA The main purpose of database system is that user can arrange a view of data abstraction. It aims to simplify the intraction between users with the system and the database can present different views to its users, programmers, and administrators. Since not all database users are well trained and users are divided into various levels, the database complexity will be hidden from the user through multiple levels of data abstraction. When looking at the database, users can be grouped into 3 levels (levels), namely:
>Physical Level (physical view / internal view). It is the lowest level in data abstraction showing how data is stored in actual conditions. This level is the most complex form, where the lowest level data structure is depicted at this level.
>Conceptual Level. It is a level that describes what data is actually (functionally) stored in the database, along with the relationships that occur between the data. This level describes the entire database, where the database administrator (DBA) builds and processes the database, while the user does not care about complexity in the physical level structure again. For example: the user will know that the sale is stored in the table of goods, production, finance, marketing.
>User View Level. It is a level with the highest level, which describes only one part of the entire database. Some database users do not need all the contents of the database eg the personnel section only requires employee file data and salary, does not require the data file warehouse, transaction goods entered.
The data abstraction level can provide an overview or view of the architecture of the Database Management System (DBMS), which will add to the notion of data independence. Data independence can be divided into two parts:
>Physical Data Independence
Ability to change the physical pattern of a database without causing a program application to be rewritten. Modifications to the physical level are usually at the time of improving usability.
>Logical Data Independenceata model Data model is a collection of concepts that can digunakakn to draw the data structure. Database structure includes data types, relationships, and some requirements that must be met database.
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