1. Define the following terms: data model, database schema, database state, internal schema, conceptual schema, external schema, data independence, DDL, DML, SDL, VDL, query language, host language, data sublanguage, database utility, catalog, client-server architecture.
2. Discuss the main categories of data models.
3. What is the difference between a database schema and a database state?
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Define the following terms: data model, database schema, database state, internal schema, conceptual schema, external schema, data independence, DDL, DML, SDL, VDL, query language, host language, data sublanguage, database utility, catalog, client-server architecture. Answers:- Data Model: – It defines the logical design of data. The model describes the relationship between the different parts of the data. DDL :- DDL stands for Data definition language defined by SQL which is used to manipulate data of RDBMS. All DDL commands are auto-committed; it means it saves all the changes permanently in the database. Command:- create, alter, truncate, drop, rename. DML :- DML stands for Data manipulation language and these commands are not auto-committed because changes are not permanent to database , they can be rolled back. Commands- insert, update, delete, and merge Database Schema – Database schema of a database system which represents the logical view of entire database and it is described in formal language. Database State :- Set of stored data in database technology is known as database state and it changes when we enter, modify or delete information. Internal Schema :- It describes the physical storage of the database. Conceptual schema :- It describes the whole structure of the database . External Schema :- It defines the user’s view of the table or structure in database technology. Data Independence :- Data independence means if there is change in the logical structure…
of database the user view of data should not change. SDL :- Storage definition language is used to define internal and external schema and it is based on relational database. VDL :- View definition language which is used to specify the user view and their mapping to the conceptual schema. Query Language :- This language is used to make queries into database and information system and is used to retrieve information from database. Host Language :- It is used to develop specified software or database applications. Database utility :- It provide interface between the database and the ABAP dictionary. Client server architecture :- It is used for user interface program and application program that runs on client side and server side and these are used for web applications. 2.Discuss the main categories of data model. Answer :- There are mainly three categories of data model. Hierarchical model :- In this each entity has only one parent but can have several children. At the top of hierarchy there is only one entity which is called ROOT> Network Model :- In the network model, entities are organized in graph , in which some entities can be accessed through the several path. Relational model :- In this model, data is organized in two-dimensional tables called relations. The tables or relation are related to each other. 3.What is the difference between a database schema and database state? Answer:- Database Schema :- It represents the logical view of the data structure and it used formal language to display this , and change in structure do not change the logical view. Database state :- it is set of stored data in database technology and changes made in modifying, entering or deleting data can change the stored data view.