Databases exam task: 1 What are the main reasons for relational model implementa

Question

Databases exam task: 1 What are the main reasons for relational model implementation. Compare RDB to legacy DB models (Hierarchical and Network). (2 points) 2. Enumerate 3 main layers of database and describe their functionality. (2 points) 3. What technique is usually employed for many to many relationship implementation, provide examples. (2 points) t in SELECT queries, provide examples of swge Explain the usage of UNION statemen and dauibte usage. (2 points) 4. Present USE CASE diagram of traffic light, minimal amount of actors -3, minimal amount of USE CASES- 10. (2 points) 5.

Explanation / Answer

Ans 1- The main reasons to implement relational database model are below-

1. Simplicity- Allows the information to be stored in the form of tables which is made up of rows and columns. This becomes very easy for the users to operate a work who are familiar with spreadsheets and workbooks.

2. Fast Data Retrieval- This feature tells us that the data which is stored in the database can be accessed in a very fast manner and can be presented to users as per their needs. The RDBMS is capable of handling larger data sets which conventional databases are unable to handle.

3. Normalization- This refers to systematic approach of finding and removing data anamolies like insertion and deletion anamolies. Moreover this approach helps to remove the duplicates in data and helps in removing data redundancy.

Ans 2-

Physical data model- This model describes how the data is stored in the system. Ex- Flat fles, NFS etc

Conceptual data model- This models represents the data in the form of set of tables.

The external Data model- It presents data as a set of relations. An external schema specifies a view of the data in terms of the conceptual level. It is created as per the needs of a particular category of users

Ans 3-

The many to many relationship can be implemented using a parent child relationship between the two entities. This concept involves a scenario where a primary key of one table exists as a foreign key in another table.

Ans 4- The UNION keyword is usd to merge the outputa of two or more select statements. The only condition which is necessary for the UNION clause is that the number of columns, the order of columns and the datatypes of the columns of the of the select statements should be same for the select statements between which UNION is used.

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