Transforming ERD into Relations

Question 1

Step 1 in Transforming ERD into Relations

Answer 1

Formally, for each entity type E in the ERD, create a relation R that includes all the attributes of E

Question 2

Step 2 in Transforming ERD into Relations

Answer 2

Representing a relationship in a conceptual ERD to its equivalent construct in the relational logical model depends on both the degree of the relationship and its cardinality

Question 3

Give me an in-depth explanation on step 1

Answer 3

○ Create a 2-dimensional table whose number of columns is equal to the number of attributes in your ERD

○ Give the table the name, written in capital letters, that you gave the entity in the ERD

○ Include all the names of the attributes in the table that you created

Question 4

how to use Binary 1:N

Answer 4

Add the primary key of the entity on the one side of the relationship as the foreign key in the relation that is on the many-side of the relationship

Question 5

This is the most common type of relationship and the easiest to represent

Answer 5

Binary 1:N

Question 6

What is Binary 1:1/ how to use Binary 1:1

Answer 6

If two entities are maintaining a one-to-one relationship, and they can share the same primary key, these may be resolved by combining the entities into one

This means that the attribute of one entity will be moved into the other and a common primary key will be established

Question 7

two entities are maintaining a one-to-one relationship, and they can share the same primary key, these may be resolved by combining the entities into one

Answer 7

Binary 1:1

Question 8

Explain merging in Binary 1:1

Answer 8

Merging the two entity types and the relationship into a single relation is only appropriate when the participation of the entity types are total (an instance of one entity type ensures the existence of an instance of the other entity type) and the entity types do not participate in any other relationships.

Question 9

when to add the primary key of A as a foreign key of B

Answer 9

If the above technique is not permissible (i.e., when at least one of the entities participates in more than one relationship)

Question 10

If the above technique is not permissible (i.e., when at least one of the entities participates in more than one relationship), the 1:1 relationship can be represented as:

Answer 10

○ Adding the primary key of A as a foreign key of B
○ Adding the primary of B as a foreign key of A
○ Both representations

Question 11

Representing Binary 1:1 Relationships

Answer 11

The designer is left with the discretion as to
which of the three is most appropriate.

Question 12

Representing Binary 1:1 Relationships (the relationship has an attribute)

Answer 12

Any attributes in the relationship will be placed in the relation or table where the foreign key is placed (which is on the optional side)

Question 13

what does Binary M:N contain?

Answer 13

Include as a foreign key, attributes in the newly created relation the primary keys of entities A and B. This combination will form the primary key of the new relation

If the relationship has any attributes, include them in the new relation

Question 14

Create a separate relation to represent the
relationship

Answer 14

Binary M:N

Question 15

Representing Unary 1:N Relationships

Answer 15

Represent a recursive relationship with cardinality ratio 1:N by simply adding a rename of the primary key with reference to the relationship

Question 16

Representing Unary M:N Relationships

Answer 16

create a new relation to represent the relationship

include as a foreign key attributes, the primary
keys of the participating entity types

the primary key of the new relation is composed of its set of foreign keys