DBMS Unit-1 Part-4 Introduction

Que1.25. Explain the reduction of ER schema to tables. OR How to reduce an ER model into table? Answer 1. In ER model, database are represented using the different memos or plates, and these memos can be reduced to a collection of tables. 2. In the database, every reality set or relationship set can be represented in irregular form. introductory rules for converting the ER plates into tables are 1. Convert all the realities in the illustration to tables a. All the realities represented in the blockish box in the ER illustration come independent tables in the database. b. In the ER illustration, Student, Course, Lecturer and Subjects forms individual tables. 2. All single- valued trait becomes a column for the table a. All the attributes, whose value at any case of time is unique, are considered as columns of that table. b. In the Student reality,Student_Name andStudent_ID form the column of Pupil table. also,Course_Name andCourse_ID form the column of Course table and so on. 3. A crucial trait of the reality is the primary crucial a. All the attributes represented in the round shape and underscored in the ER illustration are considered as crucial trait which act as a primary key of table. b. In the given ER illustration,Student_ID,Course_ID,Subject_ID, and are the crucial trait of the Pupil, Course, Subjects and Lecturer reality. 4. The multivalued trait is represented by a separate table a. In the pupil table, a hobbyhorse is a multivalued trait. b. So it isn’t possible to represent multiple values in a single column of Pupil table. Hence we produce a tableStud_Hobby with column nameStudent_ID and hobbyhorse. Using both the column, we produce a compound key. 5. Composite attributes are intermingled into same table as different columns a. In the given ER illustration, pupil address is a compound trait. It contains City, Leg,Door_No, Street, and State. b. In the Pupil table, these attributes can combine as an individual column. 6. deduced attributes aren’t considered in the table a. In the Pupil table, Age is the deduced trait. b. It can be calculated at any point of time by calculating the difference between current date and Date of Birth( DoB). Que1.26. bandy extended ER( EER) model. Answer 1. The ER model that’s supported with the fresh semantic generalities is called the extended reality relationship model or EER model. 2. The EER model includes all the generalities of the original ER model together with the following fresh generalities Specialization relateQ.1.24, runner 1 – 26A, Unit- 1. conception relateQ.1.24, runner 1 – 26A, Unit- 1. Aggregation ReferQ.1.24, runner 1 – 26A, Unit- 1. 3. The super class/ class reality types( or super type/ subtype realities) is one of the most important modelling constructs that’s included in the EER model. 4. This point enables us to model a general reality and also subdivide it into several technical reality types( sorts or subtypes). 5. EER plates are used to capture business rules similar as constraints in the super type/ subtype relations. therefore, a super class is an reality type that includes distinct sorts that bear to be represented in a data model. 6. A class is an reality type that has a distinct part and is also a member of a super class. Que1.27. What’s Unified Modeling Language? Explain different types of UML. Answer 1. Unified Modeling Language( UML) is a standardized modeling language enabling inventors to specify, fantasize, construct and validate vestiges of a software system. 2. UML makes these vestiges scalable, secure and robust in prosecution. 3. UML is an important aspect involved in object- acquainted software development. 4. It uses graphic memorandum to produce visual models of software systems. Types of UML 1. exertion illustration It’s generally used to describe the inflow of different conditioning and conduct. b. These can be both successional and in parallel. c. They describe the objects used, consumed or produced by an exertion and the relationship between the different conditioning. 2. Use case illustration Case plates are used to dissect the system’s high- position conditions. b. These conditions are expressed through different use cases. 3. Interaction overview illustration a. The commerce overview illustration is an exertion illustration made of different commerce plates. 4. Timing illustration Timing UML plates are used to represent the relations of objects when the center of attention rests on time. b. Each individual party is represented through a lifeline, which is basically a line forming way since the individual party transportations from one stage to another. c. The main factors of a timing UML illustration are Lifeline ii. State timeline iii. Duration constraint iv. Time constraint Destruction circumstance 5. Sequence UML illustration Sequence plates describe the sequence of dispatches and relations that be between actors and objects. Actors or objects can be active only when demanded or when another object wants to communicate with them. c. All communication is represented in a chronological manner. 6. Class illustration Class plates contain classes, alongside with their attributes( also appertained to as data fields) and their behaviours( also appertained to as member functions). b. More specifically, each class has three fields the class name at the top, the class attributes right below the name, the class operations behaviours at the bottom. c. The relation between different classes( represented by a connecting line), makes up a class illustration.

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