Week 1.5

Question 1

Reasons for using ISA (sub classes)

Answer 1

1) To add descriptive attributes to the subclass

2) To Identify entities that participate in a relationship

Question 2

ER Is used for what

Answer 2

Conceptual database design

Question 3

3 Basic constructs of ER

Answer 3

1) entities
2) relationships
3) attributes (of entities and relationhsips)

Question 4

Overlap Constraints:

Answer 4

determine whether the entities in the subclass collectively include all entities in the superclass

Question 5

What is a characteristic of covering constraints?

1) Determine whether the entities in the subclass collectively include all superclass entities
2) Determine whether the subclasses have different entities in the class
3) Determine whether the subclasses have permission to contain the same class

Answer 5

1) Determine whether the entities in the subclass collectively include all superclass entities

Correct
In the example, all the contract/hourly employees belong to the master employees entity which explains covering constraints.

Question 6

Overlapping Constraints

Answer 6

determine whether two subclasses are allowed to contain the same class entity

Question 7

Aggregation

Answer 7

Allows relationships with relationship sets

Question 8

Duration

Answer 8

ternary relationship

Question 9

ternary relationship

Answer 9

A ternary relationship is when three entities participate in the relationship.

Question 10

A university database records professors that taught subjects in courses. Based on the entities participating in the relationship, what kind of relationship is this?

1) Ternary relationship
2) Binary relationship

Answer 10

Ternary relationship

Question 11

What does ISA mean

Answer 11

It is a member of a higher class

Question 12

In a Database the Number of Rows are called

Answer 12

cardinality = count(*)

Question 13

In a Database the Number of Fields are called

Answer 13

degree (id,fname,etc)

Question 14

If you would like to insert a new company tuple in your corporation’s table, what is the most likely correct command?

1) INSERT INTO COMPANY ( NAME, CITY, STATE)
(“ASU CORP”, “TEMPE”, “AZ”)

2) INSERT INTO COMPANY
VALUES( 3, “ASU CORP”, “TEMPE”, “AZ”)

3) INSERT INTO COMPANY (NAME, CITY, STATE)

VALUES (“ASU CORP”, “TEMPE”, “AZ”)

Answer 14

INSERT INTO COMPANY (NAME, CITY, STATE)

VALUES (“ASU CORP”, “TEMPE”, “AZ”)

Question 15

Integrity Constraints

Answer 15

Integrity constraints ensure that the data insertion, updating, and other processes have to be performed in such a way that data integrity is not affected.

Question 16

Primary Key Constraints

Answer 16

niquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values.

Question 17

Super Key

Answer 17

A superkey is a combination of columns that uniquely identifies any row within a relational database management system (RDBMS) table.

Question 18

Foreign key database

Answer 18

A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. … The concept of referential integrity is derived from foreign key theory. Foreign keys and their implementation are more complex than primary keys.

Question 19

What is a tuple?

Answer 19

A tuple is a set of sets, defining a container with order. In SQL, it is used to represent a row. SQL uses sets of tuples to do it’s magic - model and retrieve data. Simply put, a tuple is a row in a table. A field or attribute of a table is a column.

Question 20

Why is referential integrity important?

1) It ensures a tight relationship between foreign keys in a table.
2) It ensures the correctness of data within a DBMS.
3) It ensures multiple primary keys to exist in a tuple.

Answer 20

2) It ensures the correctness of data within a DBMS.

Question 21

Ways to deal with a delete in a foreign key (data) when the primary key (data) is deleted from the database

Answer 21

1) Do Nothing
2) cascade delete
3) reject
4) Set Null

Question 22

When creating a join table use what primary key

Answer 22

From both tables to create a multiple columns primary key (they are also foreign keys)

Question 23

In the following SQL, what is/are the key constraints? 
CREATE TABLE Employees (
    employee_id INTEGER,
    badge_id INTEGER,
        PRIMARY KEY (employee_id),
        FOREIGN KEY (badge_id) REFERENCES Badge
    );
1) PRIMARY KEY and FOREIGN KEY
2) FOREIGN KEY
3) PRIMARY KEY

Answer 23

1) PRIMARY KEY and FOREIGN KEY

Question 24

sql participation constraint definition

Answer 24

t specifies that each entity in the entity set must compulsorily participate in at least one relationship instance in that relationship set. That is why, it is also called as mandatory participation.

Question 25

sql participation constraint code

Answer 25

NOT NULL,

Question 26

Weak Entity set should have

1) keys?
2) Delete super?

Answer 26

1) foreign key (part of primary key)

1) On Delete Cascade (delete if primary key deleted)