# Recent questions tagged er-diagram

1
Let $M$ and $N$ be two entities in an $E-R$ diagram with simple single value attributes. $R_{1}$ and $R_{2}$ are two relationship between $M$ and $N$, where as $R_{1}$, is one-to-many and $R_{2}$, is many-to-many. The minimum number of tables required to represent $M, N, R_{1}$, and $R_{2}$, in the relational model are ___________. $4$ $6$ $7$ $3$
1 vote
2
How to represent referential integrity constraint in ER model? pls explain with diagram
3
A university database contains information about professors (identified by SSN) and courses (identified by courseid). Professors teach courses; each of the following situations concerns the Teaches relationship set. For below situation, draw the ER diagram: Suppose ... in a team can teach the course. Model this situation introducing additional entity sets and relationship sets if necessary.
4
Here if check_txn contains its own attributes then during converting into a relational model where does its attributes will be placed either in account side ( strong entity set) or check side (weak entity set)? and why?
5
my doubt is- when question is said find minimum no.of table to given E-R diagram,and additional condition table are satisfying 1NF/2NF/3NF. how we conclude table is 1NF/2NF/3NF.
6
What is the correct answer of this Question and what are the Minimized tables ???
7
Consider the relation schemas are shown below, which were generated from the E-R diagram in Figure given below. For each schema, specify what foreign key constraints, if any, should be created. teaches (ID, course id, sec id, semester, year) takes (ID, course id, sec id, ... , year, building, room number) inst dept (ID, dept name) stud dept (ID, dept name) course dept (course id, dept name)
8
Explain the distinction between total and partial constraints.
9
Explain the distinction between disjoint and overlapping constraints.
10
Explain the distinction between condition-defined and user-defined constraints. Which of these constraints can the system check automatically? Explain your answer.
11
Design a generalization-specialization hierarchy for a motor vehicle sales company. The company sells motorcycles, passenger cars, vans, and buses. Justify your placement of attributes at each level of the hierarchy. Explain why they should not be placed at a higher or lower level.
1 vote
12
Design a database for an airline. The database must keep track of customers and their reservations, flights and their status, seat assignments on individual flights, and the schedule and routing of future flights. Your design should include an E-R diagram, a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.
13
Design a database for a worldwide package delivery company (e.g., DHL or FedEx). The database must be able to keep track of customers (who ship items) and customers (who receive items); some customers may do both. Each package must be identifiable and ... should include an E-R diagram, a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.
1 vote
14
Design a database for an automobile company to provide to its dealers to assist them in maintaining customer records and dealer inventory and to assist sales staff in ordering cars. Each vehicle is identified by a vehicle identification number (VIN). Each individual vehicle ... E-R diagram, a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.
15
Consider the E-R diagram in Figure given below, which models an online bookstore. a. List the entity sets and their primary keys. b. Suppose the bookstore adds Blu-ray discs and downloadable videos to its collection. The same item may be present in one or ... using generalization, to model the case where a shopping basket may contain any combination of books, Blu-ray discs, or downloadable video.
1 vote
16
We can convert any weak entity set to a strong entity set by simply adding appropriate attributes. Why, then, do we have weak entity sets?
17
Explain the difference between a weak and a strong entity set.
–1 vote
18
Construct an E-R diagram for a hospital with a set of patients and a set of medical doctors. Associate with each patient a log of the various tests and examinations conducted.
19
Explain the distinctions among the terms primary key, candidate key, and superkey.
20
Temporal changes: An E-R diagram usually models the state of an enterprise at a point in time. Suppose we wish to track temporal changes, that is, changes to data over time. For example, Zhang may have been a student between 1 September 2005 31 May 2009, ... and the advisor relationship, with the above extensions to track temporal changes. b. Convert the above E-R diagram into a set of relations.