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3 years ago

1. In the Entity-Relationship Model, relationships can have attributes. T/F

Computers and Technology

1 answer:

Anestetic [448]3 years ago

5 0

Answer:

1. True 2. True 3. Conceptual 4. 3 tables.

Explanation:

1. In the ER Model relationships can have attributes associated to them. For example in an organisation there is a one-to-one relationship between Employee and Department entities i.e. an Employee manages a Department and each Department is managed by some Employee. If you want to store the Start_Date from which the employee began to manage the department then you can give the Start_Date attribute to the relationship manages.

2. Attributes are the smallest division of data in the ER diagram. Attributes are used to describe an entity.For example an Employee entity can have the attributes Name, DateofBirth, Address, Salary. Attribute is represented by an oval with a name inside in ER diagram.

3. Conceptual

Conceptual level is the highest level ER model as it contains less but defines the overall scope of the model. It defines the data entities that are commonly used by the organization. A model on conceptual level of abstraction captures and represents business scope of the problem. It depicts the most important entities and the relationships between these entities. A conceptual ER model can be used as the base for one or more logical data models. Conceptual level describes or defines the structure of the whole database. It hides details about the physical storage and concentrates on describing entities, relationships, etc. It is part of the conceptual stage of database design and it provides a high-level data description.

4. 3 tables can be used to represent this relationship. One is a Student table. Second is the Class table. Now if we see the relationship. A student can take many classes. A class can be taken by many students. This is a many-to-many relationship between these two entities. It is not directly possible to implement this type of relationship in a database. To implement this relationship it has to be broken into 2 one to many relationships. In order to do this, a new entity has to be created. So create one more table to establish a relationship between Student and Class entities. Primary keys of Student and Class tables are added into new table to create a composite primary key. This table can be named as Enrollment. Hence 3 tables are used.

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3 years ago

PYTHON1.)Assume that price is an integer variable whose value is the price (in US currency) in cents of an item. Write a stateme

hammer [34]

Answer:

#part 1

#read the amount

amount=int(input("enter the amount:"))

#find the dollars

doll=int(amount/100)

// find the cents

cent=amount%100

#print output

print("{} dollars and {} cents.".format(doll,cent))

#part 2

#read a floating point

temperature=float(input("enter the temperature:"))

#part 3

#read a word

firstWord=input("enter a word:")

Explanation:

In part 1, read amount and the find the dollars with the help of "/" operator. Then find the cents with "%" operator and print both.In part 2, read a point and cast it to float then assign it to variable "temperature".In part 3,Read a word and assign it to variable "firstWord".

Output:

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enter the temperature:12.5

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2 years ago

Help! What is this graph and what does it represent?

Lunna [17]

Answer:

Explanation:

how much something had in each month in this graph

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2 years ago

Use semaphore(s) to solve the following problem. There are three processes: P1, P2, and P3. Each process Pi has a segment of cod

Lisa [10]

Answer:

See explaination

Explanation:

Here we will use two semaphore variables to satisfy our goal

We will initialize s1=1 and s2=1 globally and they are accessed by all 3 processes and use up and down operations in following way

Code:-

s1,s2=1

P1 P2 P3

P(s1)

P(s2)

V(s2) .

P(s2). .

. C2

V(s1) .

P(s1)

. . C3

V(s2)

Explanation:-

The P(s1) stands for down operation for semaphore s1 and V(s1) stands for Up operation for semaphore s1.

The Down operation on s1=1 will make it s1=0 and our process will execute ,and down on s1=0 will block the process

The Up operation on s1=0 will unblock the process and on s1=1 will be normal execution of process

Now in the above code:

1)If C1 is executed first then it means down on s1,s2 will make it zero and up on s2 will make it 1, so in that case C3 cannot execute because P3 has down operation on s1 before C3 ,so C2 will execute by performing down on s2 and after that Up on s1 will be done by P2 and then C3 can execute

So our first condition gets satisfied

2)If C1 is not executed earlier means:-

a)If C2 is executed by performing down on S2 then s2=0,so definitely C3 will be executed because down(s2) in case of C1 will block the process P1 and after C3 execute Up operation on s2 ,C1 can execute because P1 gets unblocked .

b)If C3 is executed by performing down on s1 then s1=0 ,so definitely C2 will be executed now ,because down on s1 will block the process P1 and after that P2 will perform up on s1 ,so P1 gets unblocked

So C1 will be executed after C2 and C3 ,hence our 2nd condition satisfied.

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